Disconnect the digitizer, clean the connector and the cable with 99% IPA. Make sure there aren't any tears on the flex, then plug it back in. Should fix it up.
If not, did you happen to break the digitizer connector on the board? Those connectors are kind of famous for being brittle and breaking. If so, a well placed piece of Kapton tape on the flex should keep it in the connector.
Check the flex, clean the connectors and make sure the flex is pressed in tightly.