My external drive was changed to Read-Only after Catalina upgrade

Thanks for the quick response, but I tried that previously based on other posts. This does not work.

My account is already listed as having Read & Write privilege.

Attempting to change the "everyone" group to "Read & Write" from "Read only" results in an error message as follows:

"The operation can't be completed because you don't have the necessary permission."

To provide more context, see the attached screen shot.

When I first start up or connect to the external drive, the following error modal is displayed saying that the disk cannot be repaired. Sorry, I should have provided this additional context in the original post.

Thanks, but it is formatted Mac OS Extended.