Can't set Media Folders to next external drive

I'm running iMac with Majave 10.14.

I recently installed a new external SSD drive, and copied my entire iTunes library to it. iTunes is running fine. In LMS (v7.9.2), however, I can't seem to change the Media Folders to point to the new location. It always reverts back to the previous folder setting. on the iTunes tab, I have specified: iTunes Music Library.xml Location to point to its new location on the external drive. But the Media Folders setting can't seem to be changed. Any suggestions?

Thanks.