I helped a client today that had the same issue. We had to erase the tables that Ignition creates by default and let Ignition create them again, then imported the data to those tables.
I’m not exactly clear why we had to do this but here is my theory, in the tables that Ignition creates automatically there is a configuration that makes the id column an indexed column, that means that whenever a row is added, the new id value of that row is equal to the previous row value plus one. Because this configuration was not imported, when Ignition tried to add a row the system didn’t automatically assign an id number equal to the previous row plus one, instead, it added Null to the id column of the new row, which is not accepted by the database because the id column is configured to not allow Null values.
I am running Ignition 8.1 and noticed this week that any new historian tag added was missing from the database and missing from the configuration table, I was getting the exact error mentioned here. On reading your comment I Altered the Historian Database table sqlth_te column id to have an identity Specification [Yes] and Identity Seed [1], All the failed Historian Tag Sync errors then stopped and all the new tags I had been trying to create came streaming in and all history is working now. Not sure why or how this happened but may have been when upgrading from a previous version to 8.1 a few months back
I am running Ignition 8.1.25. We had a similar issue.
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Cannot insert the value NULL into column 'id', table 'Test.dbo.sqlth_te'; column does not allow nulls.
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Resolved it by setting the "id" column in the "sqlth_te" table as the identity column then increment to 1,1.