CC app sign-in errors!!!

So. I dowloaded my paid for Adobe CC app. All good.

Was signed in under my account, as you need to be.

Then I downloaded InDesign - All good.

But when I try to open it i get this

But I just downloaded it with MY account.

I've already tried:

• deleting everything Adobe related and reinstalling everything again. Didn't work.

• As above - but with a password change. Didn't work.

• As above but with a new invitiation from the admin of the account - also me! - Didn't work.

Other errors messages I got have been:

• maximum install reached - this is a lie as i just created a new account and have only tried to install on ONE machine.

• the standard login loop that seems to befall everyone who uses adobe products!

This also happened with Photoshop.

My mac is quite old but up-to-date in terms of software/OS etc. It's also a 64bit machine so should have any issues with new software.

Any ideas anyone?