Lightroom Classic Login not working

[Pompolomo]

Hi everyone, I run Lightroom Classic Desktop 14.2 (not LRC).
By trying to start it a few minutes ago, it said "developing mode" is deactivated. I need to login. 
So I tried to log in. I had to type in my serial number, which I did - now its saying the number is wrong.

Well its the one I have from my creative cloud abo. 

My laptop doesnt support the latest LR version - so I am stuck. 
Adobe Help Center say, the version I run is still supported.

Any idas on how to solve this?

[GoldingD]

Let's skip Lr or LrC for now, although v14.2 would be classic.

Your copy of the Adobe Creative Cloud Desktop App.

Is it running (as it should) and are you signed in?

And if you are signed in, consider signing out, then signing in as a possible diagnostic, and a possible fix. That is IF YOU HAVE INTERNET. at the time you attempt this.

Note, the account (typically email address ) you sign in is the one you used when you subscribed (normally the same as used for this community)

[AxelMatt]

...

My laptop doesnt support the latest LR version - so I am stuck. 
Adobe Help Center say, the version I run is still supported.

Any idas on how to solve this?

By @Pompolomo

It seems that you Laptop' CPU doesn't support AVX2. You can check this with this tool for example: CPU-Z | Softwares | CPUID   If the CPU doesn't really support AVX2 you have to go back to Lightroom Classic 14.0.1. This is the latest version which doesn't need the AVX2. The other alternative is to buy a new notebook.

[Rob_Cullen]

"I had to type in my serial number, which I did -"  Lightroom-Classic v14.2 does not use or need a Serial Number. Serial numbers ended with version 6.14 several years ago.

You need a current paid subscription to the Photography Plan (or the new Lightroom Plan), and be signed in with the Adobe Creative Cloud Desktop App. Signing in activates the Adobe Apps.