I too have the same problem following updating to LRC 10.3 today. Import dialogue box comes up, select the folder on the LHS and nothing further happens, no files are displayed. This is on a Windows 10 (19041.1052) on a i7-9750h, 16GB, Geforce RTX. No error messages. I have also tried import into a brand new catalog and same import problem occurs, irrespective of file type (tried raw and jpg separately) and location (main data hard drive with no external drives attached, or when importing attempted from an external drive). Contacted Adobe and just got told to revert to an earlier version of LrC.