Manage Relationships not working

I have several issues building relationships using Managed Relations. I'm using the PowerBI desktop in DirectQuery mode. I have over a dozen tables taken from a database, where I've done some renaming/rearranging to the columns. I'm attempting to join them. First, the Autodetect option is greyed-out. That's not a big deal as I'd prefer to connect them manually, but I'm curious to know why.

When I select New and in the Create relationship popup, I select the table name, the first problem is the three lines of preview data does not appear for some tables, but it does for others. If I select two tables and connect on a column, PowerBI will calculate the cardinality automatically, but when I click Ok, it doesn't show any defined relationships in the Manage relatinships popup and the whole program freezes. I have to shut down the program entirely.

When I first brought these tables in, PowerBI did autodetect many of the relationships. I removed these prior to editing the tables. I planned to manually reconnect the tables afterward, but am stuck at this point.

These tables have a lot of data, but I wouldn't think that would affect my ability to join the tables. Any help much appreciated.