Have you checked that your handle hdbH is still open? you could check this with
hdbH “1+1”
or
hdbH"tables"
I wouldn’t be able to say if something has gone wrong elsewhere without seeing the rest of your code for section 3. Feel free to send me it via DM if you need some more help.
I found the problem, I think. The .perm.users table was not keyed. Once I keyed it properly, the whole exercise ran without any issues, and now I’ve got the certificate too.