Hey! Did you try the dry run or do you mean more troubleshooting than the results from the dry run?
It would be helpful if you share the results that you get from a dry run; however, I would recommend you check out this CoP post when a user faced an import issue and the solution was:
How to replace existing database's orgunits with an updated list of HFs and actually there’s a Jira issue that you might want to be aware of as well: ( DHIS2-10042 Cannot update Events with not async csv import)
BTW, what is the version of the DHIS2 instance that you are using? Thanks!