I am trying to solve the issue of not being able to Upgrade my account and I tried to remove people from my team, however I am not even able to do that. Clicking on Delete does nothing. Can anyone help please?
I will convert your post into a support ticket.
Workaround
If you don’t want to wait for the issue to be resolved, rather than upgrading an existing team, you could create a new one and then move your boards tot he new team/subscription. Once the “removing members” issue is resolved, you can remove them and just leave the Free Plan team as is, or delete it.
Creating a new team space
You can do this from your dashboard:

And then:

And, if you don’t see the above + Create team action, you may have this:

Or, by going to this page:
NOTE: You should be signed in to your Miro account before completing this next step:
Enter your E-mail address. We'll send you an e-mail with instructions to reset your password.