Hi,
a few days ago our 10.7 Portal stopped displaying content when a filter like title or date modified is set:
We could break it down to the REST Search API which returns no values when a sortField is set. If no sortField is set we get all the content like before. Our index is in sync and there are no interesting messages in the logs.
Is this a standalone Portal, or HA? If it's HA, did you stop the standby, stop primary, and then start standby before starting the original primary?