Answer:
The RF‑/FRAME‑JOINT Pro add-on module designs rigid bolt connections between columns and horizontal beams, and classifies these connections. The rigid bolt connections are designed with the ultimate load method according to Eurocode 3 or DIN 18800.
The dimensions of an end plate can be defined in the add-on module. Bolts are possible in the extensions; however, only in the extension at the top.
A bolt row in the bottom extension is not intended, which is the reason the error message appears.
You can check the minimum dimension under the design hints in the add-on module.
The desired geometry can be entered in the RF‑/JOINTS Steel - Rigid add-on module.