It can be a lot of things that affect the login, both in user and and the forum end.
I suggest that you expire your cookies here on the forum
Click on your username up to the right and scroll down to cookies.
Expiring (deleting) the cookies set in your browser by this forum may be useful if you suspect that this forum is malfunctioning for you. Expiring these cookies will do NO harm, but it will log you out from this forum. Once you log in and start using the forum again, new cookies will be set automatically.
You can also clear cache in your browser.
About yesterday we were doing loads of work with scrips and database and updated, restarted the systems due to a very old bug that was discovered.
Lots of this happened in time when you experienced your problem.
Its always best to write long posts in a notebook first and then copy paste it into the forum form. I know its easier said than done but its a fact.
I'm talking of own experience handling forums for 24 years.