Thank you so much for input. I do believe I am reasonable familiar with IT. The extraction seems to be ok, the file structure is as expected, and I checked and was quite certain that the file was not corrupted. So it was a really good suggestion from sunnyolivces running it from command line, and I got this error message:
/lib/i386-linux-gnu/libc.so.6: version `GLIBC_2.16' not found (required by ./Pianoteq 6)
My system is apparently up-to-date, and only made it to go libc-2.15.so, and as far as I can detect from googling it is not trivial to force the update.
I am only using this PC for PianoTeq, it is old and not a disaster if it breaks in my attempt to upgrade. It is more important for me to be in ptq 6, as I have upgraded my other PCs to 6 and want them to be in sync so I can use the same settings and instruments in both rehearsal, at home, and live. In other words, I am willing to try something out.
Hardware: Studiologic SL 88s + SL Mixface, Focusrite Scarlett 2i4, Lenovo Yoga I5 Windows 10 Pro
VST host: Cantabile
Other instruments: hammond (GSi VB3 II), saxophone (Selmer), harmonicas (Hohners)