Error message: unable to validate your 'Create new GDAP relationship'

For those of you struggling with this even after doing all the steps... I figured this out for me. not saying its a fix all, but give it a try.  

I too had the same issue off an on for the last couple of years. Super annoying and i have been through several microsoft support tickets. they just seem to fix it and not tell me what they did, then a few weeks later it stops working again.

when I was following the suggestion to add the partner.microsoft.com to the browser tracking exception settings ( Edge-->settings-->privacy, search and service-->track prevention-->exceptions--> add partner.cicrosoft.com) that still didn't work for me.

HOWEVER... I happen to notice that my edge profile my using my personal microsoft account & not my business one ( same email, different msft account.. I know weird). I created a new profile in edge using my business email, logged in to the partner portal and Bingo Bango.... it worked.

So even though i was logging in to the partner portal as my work email , I am guessing it was still thinking I was using a difft profile ?!?!. So the anonymous error message 715-123220 and Transaction ID: xxx was actually correct.

Now i only use edge with my work profile and dont have any issues. I'll update this if i get another error.

let me know if that solves it for you ( and if you had to add the tracking exception too )

Had this issue and the following change restored my ability to create a GDAP relationship.
Using Edge browser. Settings. Privacy, search, and services. Exceptions. (Easier just to search for Exceptions inside Settings.)
In the "Tracking prevention is turned off for these sites" option, click "Add a site" button.
Add the URL "partner.microsoft.com".

Log out of the Partner Portal, close browser and relogged in.

By the way, I eventually opened a ticket on the Partner Program and the next day, they gave me the above advice. It was a good experience with Microsoft Support although frustrating that I needed them.

We have this issue everyday with multiple engineers and admins..

Have you logged a support ticket? Partner Center Support

I am having the exact same issue. I've tried changing browsers, tried disabling adblockers and privacy settings. I've tried different networks. I keep getting the same error.

My coworker doesn't have any issues they can make all the requests and relationship assignments they want. 

I read on another forum that the issue could be connected to a user in the tenant not having MFA (potentially as specific as not having the Microsoft Authenticator app). Apparently Microsoft does random audits and can lock this down because the tenant doesn't meet security requirements. Which frankly I think is a little overboard, there are times when accounts exist but are unable to use MFA and instead we have to rely on other security measures.

I wish Microsoft wasn't so cryptic about why the error is occurring. They say to reach out with the error code but it's not like they ever reply to support requests.