I can jam and play along only single notes how do I jam or improvise chords

I'm an intermediate musician I've been teaching myself for 13 years

I know intervals chords inversions scales modes keys etc

I know how to construct all the chords invert them omit notes

It just seems when I play along to songs on guitar I can only jam or improvise single notes

I learned a lot about ear training too so I am also intermediate in relative and perfect pitch

I really feel like I could move up to advanced if I could just be able to jam play along and improvise chords