Sadly - same results - rejected as connection problem or invalid mmi code.
I now realize the very best usage for this service & SIM after re-upping with Redpocket will be if it works in a GSM GPS tracker for the person here who gets lost so very easily.
I was going to get a well-reviewed low cost tracker for her until I realized that adding in the monthly GSM costs would make it too expensive to bother with - but with the SIM already on hand all I'd need to do is renew it monthly for SMS usage only - which may be a great, final solution for all its annoyances.
The only other suggestion I can think of is to try to set up conditional call forwarding from a different handset to rule out a device/firmware issue. The FU SIM is "portable" and can be used in a different device than the IMEI registered with the line.