3:1 Trading Port Not Working in 5-6 Player Map

I was playing as blue and tried to trade my three sheep in using my 3:1 port, but the interface would not let me do a bank trade. The bank trade option didn't pop up for the 3:1, which was weird because it popped up for my 2:1 brick port in the same turn. Attaching a picture of myself on the 3:1 port with 3 sheep. Sorry I didn't screenshot the defective bank trade. I've played over one hundred games, and this is the first time it has happened though.