Unable to create a back up for my MacBook Air in an external hard drive

I have a new 4TB Seagate Portable Drive and I’m trying to create a backup of my MacBook Air running on MacOS Catalina 10.15.4 but I keep getting a message that says:

”Time Machine couldn’t complete the backup to ‘Seagate Portable Drive’.

Time Machine could not create a local snapshot to back up from.”

The Drive’s format is Mac OS Extended (Case-sensitive, Journaled)

does anyone know how I can fix this?

Any other way I can create a back up?