Please try this if I you have not enrolled in Extended Security Updates.
1. Create a Microsoft Account here
https://account.microsoft.com/account
2. Log into onedrive
https://onedrive,live,con
using MS account id and password
Just put some scenic pictures(no faces if you are concern with privacy) into your onedrive.
I managed to enroll in Extended Security Updates with the above with signing into my PC onedrive. Then again I think I am already sign in because I click on my PC onedrive app and I can see all my items on onedrive.
Go Check Updates and do all the updates and see if the enroll button is there.
If still cannot then you have so click on the onedrive icon in your taskbar and sign in using your Microsoft account. You should be able to enroll now.