@Roman Klimenko's answer did not work for me, but pointed me in the right direction.

My Indexer Service was running fine, sort of. The logs showed a lot of thrown excpeionts all over the place. It turns out my Solr service itself had entered a paused state so it was Solr rejecting all connections to it.

In my scenario, it was down because of a change in the Java path for the Environment Variable due to a recent Java update, but in general if Solr is down the search against the collection will throw a similar exception.

@Roman Klimenko's answer did not work for me, but pointed me in the right direction.

My Indexer Service was running fine, sort of. The logs showed a lot of thrown exceptions all over the place. It turns out my Solr service itself had entered a paused state so it was Solr rejecting all connections to it.

In my scenario, it was down because of a change in the Java path for the Environment Variable due to a recent Java update, but in general if Solr is down the search against the collection will throw a similar exception.