Check if the products are still assigned to the correct customer group. You can do this by editing the product and checking the "Customer Group Price" tab.
Check if the group pricing module is enabled. You can do this by going to Stores > Configuration > Catalog > Catalog > Price.
Check if there are any conflicts with other modules. Try disabling other modules one by one to see if that resolves the issue.
Check if there are any errors in the logs. Check the exception log and system log for any errors related to pricing.
Try re-indexing all the indexes. This can be done by going to System > Index Management and clicking the "Reindex All" button.
