@ridhijain
Thank you so much for your response!
The solution that worked for me was changing the date and time (something like 06/03/2017) of the desktop computer. I've successfully installed and tested the program again, with (apparently) no issues. Then changed back the date and time, opened the now installed program, and it still works! I'm going to actively test and supervise it in case it shows some kind of weird behavior or issues.
The other two solutions (mentioned in the Workaround section of the link you gave me: keyboard shortcuts & new directive) didn't really work, since the installation error message appears again. And I can't re-sign the certificate since... you know... I'm not the application author
I can continue with my maintenance process! I want to give you a big thanks for this one. It really helped me a lot and I didn't know that was a solution for a seemingly weird error.
Thanks a lot!
