Can I still upgrade my Windows Phone 8.1 to Windows 10 Mobile this day?

[rhrhd]

Hi. My phone is Lumia 640 XL.

I have tried Upgrade Advisor App, it tells my phone is eligible to upgrade.
Then I go to phone update from settings, check for updates.. then it shows error code 801881e1.

Can someone tell me how to do upgrade today? is it still possible?

Thanks..