What version of Couchbase are your running on. If you are on version 4.6.2 or earlier then this is a known issue and is fixed as part of release 4.6.3, try upgrading to 4.6.3.
Restarting the indexer.exe should also fix this. Can you try and let us know if this helps.
We had a similar issue with the following message in the Logs and worked with support team and this is fixed as part of MB-25253.
Warning: Cannot communicate with indexer process. Information on indexes may be stale. Will retry