Sorry to reply to my own message.

Duh! I figured it out.

Per the documentation for the embedded server:

"Just copy fbembed.dll into the directory with your application. Then
rename it to either fbclient.dll or gds32.dll depending on your
database connectivity software."

I was using the fbclient.dll from the normal installation, not the
fbembed.dll renamed to fbclient.dll.

thx