Well it could be that yor software did not use the "baseline" Jpeg compression scheme. The JPEG Standard includes over 20 different encoding schemes for compressed pictures, and most of them require the software company to pay fees for their use! The same is true of JPEG2000. Even the "Baseline" compression scheme is patented, but the committee negotiated to use the "baseline" algotithm royalty free. The other allowed schemes require fees.
If the Forum software cannot load your file, try reloading them into the original software package and use "baseline" Jpeg compression to store them. Better to find out now before you save and disseminate a lot of compressed images that few others can read.
Wow, if enlargers were invented today, some company would patent the process and require that we pay royalties to them every time we use it.