The software needs to make contact with our License (web)server + database to check your license if it's valid and not a pirated version. If it can't contact the license server, for example if you're not connected to internet then this error will be shown.
As you can read at the webpage (FDOK + MR1 Calculator), when you scroll down you can clearly read the text:
** Software requires internet connection for license checking (anti crack protection).
Our software works without dongle and is not hwid locked (you can run it on any system), but it requires internet access because of all software can be cracked/patched in memory and there is no way to protect it without online license check.
In case you're offline:
As temporary solution you can ask someone to run it on a system with internet connection and call them over phone to give input and ask them for output.
In case you're already connected:
Maybe your firewall is blocking the file, in that case you need to put the file in "trusted" or "whitelist". If it still doesn't work then it could be caused by OS configuration settings, try to run the calculator on another system.