I have a similar issue.
Previously I created (and/or found) logos for each table and dropped them in my "Real DMD Color Images" folder. As I scrolled through the tables in PBX the matching logo would display on my PIN2DMD.
Last week I upgraded my PIN2DMD firmware from v1.76 to v2.55, and my install of PBX from v2.50 to v2.86.
Since these upgrades PBX shows only a blank black DMD all the time when in the selection menu. The DMD displays correctly when playing a table in VPX, but then (most of the time) returns back to a black DMD again when I exit back to the PBX menu. I say "most of the time" because occasionally the DMD just stops mid-animation when I exit a table and stays showing whatever was on it until another table is opened.
Because I stupidly did both upgrades together - instead of one at a time with some basic testing between - I don't know which upgrade might be the culprit. I've checked through the config of all the software and no settings seem to have changed. I'm suspecting a PBX config thing somewhere, since it's only in that app that the PIN2DMD ceases to respond.
I've tried copying in newer XDMD dlls as simbamame and vanion mentioned above, but with no change of behaviour. Beyond what I've already done I really don't know what else to try. I don't really understand which dlls are used to achieve what, or which folders PBX and VPX each go looking in for DMD files.
If anyone has any ideas I'd appreciate it! I realised it's only a cosmetic thing to get the logos displaying, but it kind of bugs my OCD when something which used to work doesn't any more :$