There appears to be another GMB related bug. Sporadically some users are not able to leave a review for a business the find via search & local knowledge panels. They also are sometimes unable to leave a review when given the GMB Profile Short Name URL.
Users are reporting that the tap or URL that is supposed to open up the review window is not working on mobile. I checked a few examples and it seems to still work on some listings but not others.
Here is an example of one that does seem to be working on mobile.
For this one, the shortname URL takes a customer directly to the review box where they can select a star rating and leave a review.
However, there seems to be a bug where some taps or shortname URLs do not open the review box. Instead, Google takes the customer to their general knowledge panel or a box where stars show but no review text box is present.
What are you seeing for your business or clients?
GMB is aware of the bug and we will post an update here when resolved.
For a full list of GMB bugs see - Current Google My Business Technical Issues/Bugs – The Expert's Guide to Local SEO