You would need to dig into the logs to find out. Just a general note on that, you need to import groups before users. Group membership live on the AD User object so groups need to exist before you import users.
Take a look at the OpenIAM logs and see if you get any errors. Also take a look through the AD Powershell Connector logs to see what’s going on. Need to get an idea of what errors or logs you are seeing to take a guess at what’s going on. https://docs.openiam.com/docs-220.127.116.11/connectorconfig/microsoft/2-powershellconnectorsusage will show you how to view the connector logs.
How many user objects do you have in AD? Did you try reducing the scope of your search query to a single user to see if it imported it?