Allowed character limit reached

I have been using NMT with SDL Trados Studio 2019.   I received a notification stating that allowed character limit reached.

There is a link stating Check MT subscription.  But clicking the link generates only "Page Not Found."

Does the character limit reset every month?  When will be reset in my case so that I can use NMT again?

Can I increase the character limit by upgrading/paying for a subscription?  If so, how?