Error attempting to manage tools

I am  running a test installation of Moodle (3.8+) to help with developing an LTI 1.3 tool. When I go to Site Admin: Plugins: External Tool: Manage tools, I get an error "invalid response detected". With debugging turned on, the stack trace shows "Missing following required key in a single structure: platformid"

I'm not sure if I missed some step in setting up my Moodle, or what.

Anyone have any ideas?

I suspect this may be interfering in working with the LTI tools I am trying to set up.