Glad to help. But I can't think of any reason why 3.11.10 would work in Lupu 525, but NOT work in 528. Again, my hplip_scan package is self-contained - you don't need to download anything else, unless you want Simple Scan. There is a PET available for it somewhere in the forum.
FWIW, I notice that james186282 above reports a scanning problem with his C310. The latest release of HPLIP has patches for that model, so 3.12.9 might work for him.