You may have to restart and also choose to run Disk Utility on the hard drive of your Mac.
• Disk Utility User Guide for Mac - Apple Support
https://support.apple.com/guide/disk-utility/welcome/mac
Note sections, last one in particular: How to repair a disk
Safe mode on startup, can be done w/o Disk Utility, too.
See blue-text link below.
The later macOS has different file structures and uses space differently. So sometimes
that may get tripped up. To start Mac in Safe mode, which also helps system files and
sort some things out in the background, and re-start to exit Safe mode, helps too.
And you may have to consider updates to Catalina macOS 10.15.(2?) as 10.15.4 had been
available for awhile; and some users were able to update that to last step, 10.15.(.5?)
While none of my Macs is upgraded to the most recent macOS; some of these only
run only vintage versions of Mac OS X. I no longer run 'the latest macOS'. One has
Mojave 10.14.6; and another Mac has dual hard drives, so also has more than one OS.
(Late PPC G4 Macs and early Intel Macs are still in use here, too.)
Good luck & happy trails!🌞🎣