Captain Cadaver said:
To be fair, his anime self was beaten by SSJ Galu and Freeza after becoming fatigued, so being pushed back by the two Base Saiyans isn't entirely impossible if he lost the same amount of power in the manga when the gap between Base and SSJ doesn't seem to be much different to what it is in GT.
This is significantly lamer since Vegeta wasn't even explicitly defeated by Jiren, Galu saved him before Jiren could KO him out of SSJBE and Jiren himself sustained far less damage than his anime self had against MUI Galu, being the one who won the exchange instead (whereas the anime version was soundly defeated before Galu collapsed).
If not Galu, Vegeta should have transformed at least imo. He's basically rested the entire time Jiren was out fighting Freeza, 17 and Galu and was never KO'd to begin with.