First could you try a soft rest: Push and hold down volume and power button for 10 seconds, then it will reboot.
If that do not solve your problem consider making a hard reset, that could fix the issue but you will lose all data and media stored in the phone.
How to reset.
Another option could be using the Nokia Recovery tool, you will need a PC to run the software. With the Nokia recovery tool you can install the latest firmware version for your L925 which is Cyan, it will install WP8.1 too.
*You may want to wait a couple of days before using the Nokia Recovery tool, because it seems the servers are down so no chance to download the updates until they put the servers back online.