What should be done if a warning is received in the VTs Log file saying "connecting problem to the distributor"?

There may be a connection problem between VTS and Distributor.

Check the "DistributorIP" field and related ports in the appconfig file of the VTs. If you are using any virus programs or firewall software, make sure that you have defined the appropriate rules.

Check the SQL Server service is running and the storage capacity is sufficient.