External user sharing to personal gmail users has stopped working

I'm at my wit's end here. I have a report that has been shared with a variety of external users, utilizing Azure AD guest users (Azure B2B). Every one has a PowerBI Pro license assigned to them. Some are External Azure AD, and some are personal gmail users.

Here is the workflow:

- Invite guest user from Azure AD

- User accepts invitation

- A PowerBI Pro license is assigned to the guest user in Azure AD

- We give them access to the dataset, assign them to RLS security, then finally share the report.

- We email the user the link "https://app.powerbi.com/home?ctid={tenant_id}"

Ths has been working perfectly for over a year. Lately, none of the gmail users can access their report anymore. Nothing has changed, but when they click the above bookmarked link, it redirects to the Power BI homepage, and when they hit sign in, it gives the famously infuriating message:

you can't sign in here with a personal account. use your work or school account instead

Has anything changed, or does anyone else do this and know how to fix it? I've tried multiple browsers, clearing cache and cookies, and no help. The MS docs still list personal emails and gmail specifically as supported account types.