I bought Minecraft Java years ago for PC. When launching game, Mojang does not recognise my account... Even though I am already signed into it.

I have downloaded, uninstalled, re-installed, and launched Minecraft Java edition multiple times. Eventually, it required me to re-purchase Minecraft. Which I did. However, all that did was charge me, then return me to the launcher. It asks for my email & password. Which is the same email & password I am logged into with both Microsoft.com Microsoft.net & Mojang.com .... yet it gives error "invalid email or password used"... PIHHWEFHWEPHNJCDNCWE!!!!!!!!!!!! 

Apparently there is something that broke with my account during the migration. Which I am now stuck in a loop where re-purchasing the software game still does not fix the issue. Please advise?