Conor McGregor -- M.I.A. At UFC Presser ... [Update: I'm Here!]

The UFC 202 press conference just began in Vegas ... and Conor McGregor is NOT there.

Dana White is pissed ... and started without him, saying the fighter has no respect for anyone's time.

Nate Diaz said Conor is "rude."

Of course, Conor's issues with his media obligations for UFC 200 triggered a war with UFC earlier this year ... but it seemed like the two sides had worked things out and were back on the same page.

Apparently not.