Ensure the file name is dotnetfx45_full_x86_x64.exe .
If possible, install .NET Framework 4.8 (the latest, supported version) instead. Most apps written for 4.5 will run perfectly on 4.8. The offline installer for 4.8 is ndp48-x86-x64-allos-enu.exe . download dotnetfx45-full-x86-x64.exe offline installer
Let us know in the comments if you encountered any specific error codes during your installation, and we’ll try to help troubleshoot Ensure the file name is dotnetfx45_full_x86_x64