Here's what I'm doing step by step (and I've tried it tons of different ways to try and make it work

):
-I extract the downloaded file into my downloads.
-I run realflow_v5_0_1_0152_x86_64.exe as administrator and install it.
-I take RFGUI_x64.dll from the crack and move it into my realflow 5 install directory, replacing the one that was already there.
-I delete the demo_license.txt file in my realflow 5 directory.
-I move my license.txt file located in the download into my realflow 5 directory.
-I run realflow 5 as administrator.
-I instantly get greeted by a small grey box, telling me "No valid licenses were found".
-I click ok.
-I'm greeted by a grey realflow license box, with the options "New license" and "Remove license" on the right hand side of the box.
-It's important to note that there's already a license listed in the license manager, so I click remove to get rid of it.
-I then click onto New license and then select "from file..." (although the result is no different if I copy and paste the text directly), and select my license.txt.
-When I click ok realflow tells me it's an invalid license - and that's as far as I get.
Thanks for the answers so far, I'd appreciate if any has any fresh ideas they let me know - I used to use realflow 4 without problem.