Slitherine

I cannot reiforce some units even after placing them in a victory and city hex - any ideas why please?? Currently playing Stalingrad but has occurred in other scenarios

What does it say if you hover your cursor over the reinforce button?

It says Unavailable Equipment pool for this type is empty. I tried deleting on unit & that gave me a bit to reinforce another. Assume I need to figure out how to put some units into reserve to enable me to reinforce others?

I think that should concern only captured vehicles. Maybe you're using some kind of commander trait that limits the reinforcement?

you are playing with "industrial connection"
the tiger1 for this battle (stalingrad) is a prototype, you have simply exhausted the number of prototypes available, as probably for your other fights

Looks like you maybe right 2 of the units were Tigers & the other two were Panzer IIIL