I read other questions regarding this issue and went into Terminal to follow the solution, typing, "sudo apt-get install exfat-fuse exfat-utils". This is the error I received, which incidentally also happened near the end of my upgrade to 19.10:
Closed all other Terminal windows and still the same error.
N: Be aware that removing the lock file is not a solution and may break your system. E: Unable to lock the administration directory (/var/lib/dpkg/), is another process using it?