I just inherited management of three websites for a new client. The previous agency did not add her as an admin to any of her sites in Google Search Console, Google Analytics, or Google Tag Manager. I am in the process of fixing this.
I am an admin on her GA and GTM accounts, and a owner of her web properties in GSC (via delegation).
She is now an admin in GA and GTM. I was able to successfully add her to GSC as an owner to one of her properties by delegation, but on the other two I get an error message:
We weren't able to add firstname.lastname@example.org. Please try again later.
What can cause ownership by delegation to fail, especially when it works on another property? As a stop-gap, I can see if I can get her to verify ownership herself with one of the other methods, but I would really prefer the delegation method.