I am running Catalina 10.15.3 on a mid 2015 MacBook Pro. I am trying to use BlackMagic's Disk Speed Test app v3.2 to test the read and write speed of the internal SSD. I am logged into my user account on the MacBook and it is an Admin account. When I try to run Disk Speed Test I cannot select the internal SSD on the MacBook. I get an error saying it is a Read Only drive. I tried using the Get Info window to add my user account but get the error message in the attached screenshot that I don't have the necessary permission. I also tired changing the "admin" listing in the Get Info window to Read & Write but I get the same error.
What am I missing?