Can't access /wp-admin - does anyone know how to fix?

I'm having an issue where I can't log into my site - in the Chrome browser in case that makes a difference.

When I go to I get a sign-in box (see attachment) - which no matter which signin information I use (be it admin or lower levels of membership) it rejects the information, even though it's correct. It didn't used to do this, and I'm unsure of what has changed.

Initially I freaked out thinking that I couldn't access my site ever again, but it turns out when I use a different browser (Epic browser in this case), I get the same box but with different information required (a system generated username and maths question password) which DOES log me in.

I don't understand what has changed or how to fix this problem so it either a) goes back to how it was or b) at least accepts the (correct) login information I'm using and let's me into the WP dashboard. Having to do everything in Epic browser where none of my history saves is massively frustrating not to mention time consuming.

Any advice would be hugely appreciated :slight_smile: