I have the exact same issue and cant use the trial workspace properly as any new “pupil” level user is getting security prompts when trying to login. Google help agents have told me that this wont happen when the school is approved but I have been waiting 3 months already and this morning they extended the trial until March 2026! The school has invested in chromebooks and licences for older devices I have converted to ChromeFlex. At present cant use any of them properly. Only solution has been to setup managed guest sessions