But which redistributables? As it says in the documentation, you need to install the latest combined (i.e. for 2015-2022) redistibutables for both x86 and x64. Did you install these? If so, please let me know your order number and I will check your details here. Do not post your key details.
Please note that EVERY report I get on this is down to user error, usually either by not entering the correct details (all 3 parts, name, email/address, key) must match exactly, or due to not having the required redistribtable packages installed.
You can also try manually creating your key file (as shown in the Installing and Registering FSUIPC document) and then running FSUIPC7 to see if the license is recognised. If it is recognised by FSUIPC7 but not validated by the installer, it will be due to either your VC++ redistributables or anti-virus software.
John