I have a similar issue. When I right-click and select Bump Fee, nothing seems to happen. No dialog appears, and nothing extra is written in File > Export Log File....
The transaction has 1 input and 1 SegWit output. It looks like it never got propagated to the network - there was a warning about P2P/RPC when I created it, and Blockchain Info says "Transaction not found" more than half an hour later. I'm using Armory 0.96.3.99, and Core 0.14.1. So it may be that this behaviour is as designed; if so, the user experience is not great.
Later: I used Help > Clear All Unconfirmed to get rid of it. Resending with a higher fee had the same problem. I'm going to try updating core to 0.15.1. If my node isn't well-connected enough, is there anything I can do to improve that?