I would check the starter motor voltage itself firstly and work backwards into the feed circuit. The relay coil maybe operating but the contacts are faulty.
Diagrams are on
gomog which are as accurate as any Morgan fuse card

Good luck
Thank you for the tips. It sent me off in the right direction.
The relay was working, but there was a bad contact in the wiring to the relay. So no current to the starter motor.
It turned out to be a cable going to the starter relay that had moved a bit when I was fiddling with the cooling fan relay next to it.
So even if the relay was fully seated, there was bad contact to the relay.
I pushed that cable into it´s correct place and then the car started.
Happy happy, joy joy.