Some ships are too large to squadron with more than a couple small fighters. If you have heavy freighters you might not be able to squadron with other larger ships. If it does not violate any sort of security protocols, a little more info might be of some use to us.
Anyway the various guides will be talking about the old squadding method that required all the ships to be the same type and only fighters and select freighters. I would guess that that is still around, but the new squadding functionality is much more powerful.