I'm wondering if the refusal to grant immunity is the Republicans way to impede the investigation.
It could be any number of things. First, maybe he doesn't have anything worth granting immunity for; whatever he's willing to testify to doesn't get the bigger fish the investigators are after. He could be telling the truth or he could be lying, but either way, granting immunity isn't appropriate. Second, it's possible they have enough without his testimony to proceed, and they think they can get him anyway. Hopefully that's the case, but hope in one hand, etc. Or, like others said, it's a media strategy by Flynn and his lawyers. I have no idea what such a strategy is, but I know exactly dick about media strategies.
Whatever the case, this is disappointing. Or maybe me wanting to see the Orange Buffoon strapped to a rocket and blasted out of office ASAP clouds my judgment.