Adobe ID problems and access to library eBooks on Kobo

Adobe Digital Editions is not letting me authorise using my Adobe login, telling me I cannot use the login if it has been used on a previous device.

Furthermore, it is not allowing me to read books from Overdrive I have borrowed from my local library, and transfer them to my Kobo eReader. I had NONE of these problems as of yesterday, and trying to solve them has made them worse.

I have tried ALL solutions I have found online, and have contacted Adobe and Kobo. Adobe advised me to post this on the forum.