So in other words I have to install Win 10 to use MP3tag with Discogs?
You should stop using Windows7 for your own safty...
Windows10 upgrade is for free 
So in other words I have to install Win 10 to use MP3tag with Discogs?
still better than using OSX 
Well, ever tried mp3tag under wine? Linux Mint would be an possible replacement for Windows7
I wouldn't rush things and maybe wait a few days till we get an official statement from Discogs staff. However, if you were at the verge of installing Windows 10 anyway, it's probably a good motivation to do it now.
FYI, I've also reported the issue on the Discogs forums and just noticed that the topic isn't visible unless logged in (for reasons that are not transparent to me).
hope nobody still using windows xp
Today, 7 pm in Argentina with mp3tag v3.00 is working!!!!
Works for me as well now. Great! 
Yep, fixed on my end.
I gave my reasons above why I don't want to do a fresh install & now I don't have to.
In the forum of Mediamonkey, someone wrote.
Discogs had updated the ciphers across the board to their servers - including the API services - which is what was causing the problems.
They have reverted the changes to the API services, which has restored functionality for the tagger in MM4 on Windows 7 (& Windows 8 presumably)
You can view the threads here... https://www.discogs.com/forum/thread/809378
And here... https://www.discogs.com/forum/thread/809470
I assume, Mp3tag should work again with Discogs too?
Yes, in the topic where I reported this issue eknudtson from Discogs staff explained
This went out accidentally with an upgrade to one of our internal components (they changed the TLS cipher suites allowed).
All is back to good again and everyone affected got a kind reminder, that things are probably getting more difficult as Windows versions grow older.