Ignoring “come here” / recall

Hello everyone! I have a 4 month old puppy and I’m a newbie dog owner. I realize that I’ve been saying to him “come here” a million times now and he doesn’t listen. After reading a bit on the recall training I realized I never properly taught him what I expect from him when I say “come here” and now he completely ignores it.

Should I try to teach him “come here” again from the beginning or should I pivot? Any tips on how to teach a puppy recall?