I would double check that your tag historian/ tag history provider is configured correctly and also confirm that the DB connection that your tag history provider is using is not faulted/disconnected.
Copy the full stack trace for each error and paste them here as preformatted text, see Wiki - how to post code on this forum.
The stack trace normally has more details as to what exactly caused the error. Sometimes the error messages also have a magnifying glass icon that you can click/hover to get some more identifying details, depending on the error type and source.