Yes, I said in many threads we know it's possible that having the P3D version previously installed might cause issue.
More precisely, is not SUPPOSED to cause issues because, the moment you install GSX Pro, the updater will download all the latest files, which are designed to be cross-compatible with both. The issue is, if your local cloudflare node is stuck with the old P3D-only version of a particular piece of code, the updater won't get the new one, and this surely cause issues.
Installing the P3D version before might fix the problem or not, depending if your local cloudflare node is fully updated or not. In fact, if we could be sure all cloudflare nodes are ready, the installation order won't even matter, because the Live update which is ran as the last step of every installer would surely update everything to the last version, no matter how old your P3D installer is. That's because even the updater program *ITSELF* is downloaded in realtime by the whatever old P3D installer you have.
However, since it seems that for some users the problems are still happening, it means the whole cloudflare network hasn't been fully updated yet so, IN THE MEANTIME, we can offer the following suggestions:
- Install GSX Pro after GSX and GSX L2. In fact, any other installation order can simply summarized as "install GSX Pro LAST"
- If that still doesn't work, and you have errors you are not normally supposed to have, like the one reported by so many users in line 411 of GSX (which is 100% sure it's a server problem, since that line doesn't contain that code anymore now, so it's coming from an old file), if you remove GSX for P3D, possibly also clean up the Addon manager\Couatl and Addon manager\Couatl64 folders as well, and install just GSX Pro, it should get you going in MSFS, at least. This while you wait an update for the P3D full installer, which will contain all the latest files, so it won't install old stuff in any case.