I have a problem with Meraki MX 14.39, Meraki is blocking users' internet access, ignoring group policies and sending them to the default rule, blocking all access. When you put the proper users into groups manually it works again. Has anyone ever had to deal with such problems?
Nope, we definitely do not have that problem. It sounds like you have a misconfig somewhere with a rule that is tripping you up.
Do you have any GP's applied to the VLANs?
GPOs are applied in groups and not in VLANs. Each user applies to a specific group and there policies are assigned to that user.
So it sounds like your MX has forgotten which groups the users belong to, then? Has anything changed on your MX recently? Did anything change with your user groups?
Do you remember how users were originally assigned?
Via Active Directory.
How is group policy assigned to the users? Manually? Via Active Directory?
Yes, Via Active Directory.
By the logs it is blocking in the rules of Content Filtering and it is not respecting the policies of the Groups that is linked with the Active Directory.