Just registered to post that this worked perfectly for me. My Q,W,Shift and many other keys would not work. My touchpad worked fine, and the weirdest thing was I could straighten out the back bendy part of the keyboard and the W key would work. Opening up the bottom, detaching and reattaching the ribbon cables, and placing a piece of black electrical tape over the connections (just in case) solved all my problems. The weird thing is one of the flex cable connectors for the large black ribbon cable was open, and one was closed. That's probably not a good thing!
I used a guitar pick to unleash the hooks. It was thin enough to easily slide in, strong enough to be twisted to apply force, and wouldn't tear through the plastic like I felt a flat-head screwdriver would. It was easy enough to open, and easy enough to close all the hooks back in when I was finished. Thanks random internet forum found through Google!
I'm on my 3rd keyboard, all replaced under warranty. However the warranty has run out and this one has now gone faulty. Unfortunately the technique above didn't work for me. I've disconnected and reconnected all the cables to no avail.
The 2520 detects the 2nd battery and USB works ok but no response from the keyboard. Is there anything else I can try??
What an amazing find!. This was my 3rd power keyboard: on the first, the keyboard worked, but the battery wouldn't charge. On the second, the keyboard didn't work, but the battery and USB worked fine. On this one, for which I got a refund for from the seller, the battery charged, USB worked, but the keyboard was flakey as hell. The combination of advice seems to have solved the problems. Use a guitar pick to open the back, maybe with an assist from a small flathead. Pull out the cable using the pointed instructions for the flex connector. Reattach cable, and apply some electrical tape. When marrying the tablet to the keyboard, apply a little wetness (licked fingers work) to the keyboard connector side. Voila! Mirable!
I fixed my flakey keyboard by restating the cable! One comment. The connection is a ZIF (zero insertion force) connection. You pull the small white parts on both sides of the connector slightly towards the cable to release it, and after reinserting the cable, push them back away from the cable to lock the cable in. If you do not lock it in place it will not make good contact. I sure which I knew this fix before I bought another keyboard off EBay (that does not charge!) Now if only I could find a replacement battery in stock at a reasonable price!
Indeed I had exactly the same problem: suddenly some keys of my SU-42 keyboard were not working anymore (the ENTER, the 'p', the 'e', etc.). It was very strange because it did not receive any hit nor it didn't fall, so this happened suddenly without any special reason that I may be aware.
I first tried to uninstall and reinstall its drivers but it didn't work. Unfortunately it was quite clear that it was not a SW problem. I thought that maybe it was some kind of battery issue, but it didn't make any sense. So I was giving up when I had the chance to read this post, so I decided to follow the "oliverr871" and "derrickg02" indications.
The first step is to remove the cover and unfortunately in my case it was not so easy: I had to use an old plastic credit card to pull gently the back, little by little, starting in one of the USB's side, and moving around pulling all the cover. I had to do apply some strength until the internal tabs started to be removed with a peculiar "click" sound. Finally I could remove totally the back cover to access the electrical part of the backside of the keyboard.
In my case, I did not notice any problem with the black flat parallel cable and at least it seemed to me that it was perfectly connected to its mother connector. But as "derrickg02" recommended, I decided to remove it in order to clean it and then reconnect it to ensure that it was really correctly connected.
It is important to highlight (as "robertre" explains) that it is not needed to do any strength to unplug this flat cable. I was a little confuse because I thought that I had to pull up the connector in some way. Do not do that! It is much more simple. You only have to remove its orange transparent sticker and then you only need to slide gently the cable towards yourself. It has a white removable part that acts as clip and that will be removed too, so the black flat cable will be disconnected easily. I include some pictures to show how the cable is when it is removed from the connector.
So then I cleaned the connectors blowing on the connector to ensure that there was no dust inside. I put again the white removable clip together with the flat cable inside the connector. I pushed with a little of strength to ensure that now all the connectors where correctly connected again. To be sure, I connected the Lumia 2520 tablet and tested the keyboard before reassembling its back part. And yes, finally all the keys were working perfectly again! So I put again the orange sticker on top of the flat cable (at the end, I used a new sticker) to ensure that it was not moving away from the connector again, and then reassembled its back cover.
Now I'm enjoying again my great Nokia Lumia 2520 with its SU-42 keyboard working perfectly! I'm very happy because I have been using them for the last 5 years and they have been working as a charm until now. I know that such tablet is quite old for our nowadays standards, but the fact is that it has been working perfectly for my needs. Specially when I travel for meetings or on weekends and I don't want to carry my laptop. With the tablet battery and its keyboard one, I can use it few hours without any problem. I mainly use it to read emails, to take notes in OneNote or edit Office documents that I download from my OneDrive account. And of course, also to listen music, watch offline videos, or to browse Internet. Yes, I know what you are thinking: we are in 2020 and there are much better new W'10 tablets, but honestly, why do we have to renew our electronic devices so often if our actual devices work perfectly? In my humble opinion, it is a shame for those companies that use Marketing arguments to convince us to renew our devices each 3 or 4 years. Programmed obsolescence in software and hardware should be totally banned and forbidden. Nowadays it is very clear that such behavior is not sustainable for our environment. So here I am with my nice Lumia 2520 tablet hopefully for many years more!