If you are using G2 version 2020.3 or older, it is possible that the GSI variable values do not get updated when you restart the OPC bridge. This article provides information on solving this issue.
This is a known issue that was caused by an error in handling some OPC timestamps, which would prevent the propagation of OPC item values. As a result, after restarting the OPC bridge, some GSI variable values would not be updated. This issue was fixed in the release of Gensym version 2020.4 (release notes) and does not occur in any subsequent releases.