Some people seemed to have the same issue in this thread, could you see if any of the suggested solutions work? It seems like for some people, copy-pasting the data worked despite not being able to see the input.
In your browser, open the inspector (F12) go to Storage and toss away all your Mendix cookies.
When I had issues logging in, I used WhireShark to read the network communication between my client and the server. I found out that the way our company's proxy server changed. If you have a proxy server that requires authentication, please fill it in using the link on the login screen.
If you record the network traffic using WhireShark and you need help interpreting it, you can ping me here.