Can't log in to WPMU with my username or password

Hello,

I have been having great trouble logging in to WPMU the past few months. Sometime I can. Other times I can't. I'll enter the correct username and password and it will redirect me to the home page.

I can only submit questions using the WPMU DEV dashboard plugin installed on my sites.

Can someone please advise on how to correct this?

Thank you.