I understand you are using PItoPI connectivity to replicate data from the Primary Collective member to the Secondary. This worked a while ago but doesn't work for all tags currently.
You didn't find any related messages in the logs. What logs did you check?
Also please verify the configuration of tags on the Secondary PI Server for a tag that is currently receiving updates against one that is currently not receiving updates. Please look for differences - especially for the point source attribute and the interface ID (Location1 attribute).
Please also consider opening a call at OSIsoft TechSupport. The colleagues can support you in a remote session and you can send them relevant logs for analysis.