Site Kit Can’t Connect to Tag Manager (Works for GA)

Hello, I set up a GA account for a client and then installed Site Kit to connect it to their site. That worked fine. Another party created a Tag Manager account and added me to it as an admin (using the same email I am using to connect to GA), so that I could try to connect it to the site, too, via Site Kit. However, I continue to get a notice to “Re-fetch My Account” when I try to connect — it’s clearly not connecting. When I try to connect, I get to a page that gives me the option to “Create an Account” or “Re-fetch My Account.” I don’t want to create a new account, as one has been created already. But clicking “Re-fetch My Account” doesn’t get me anywhere — it just refreshes the page.

I’ve tried disconnecting my Google account, trying other browsers (in case it was a cookie issue). Thoughts?