There are several things that could cause this.
If you've ever had QTP/UFT installed on the machine, and it's license is expired or invalid, then it may prevent the free trial from working, depending on what type of license you had for that. You can only get a trial license from Micro Focus sales.
Some other things that could cause this are permissions and clock tampering.
Ensure that you have full permissions to your LeanFT installation folder and all its subfolders.
Ensure that you have not changed the system time. If you have moved the system time, the license mechanism can reduce the trial period based on the number of days that were back-dated.
You can find more information [here][1]
[1]:https://admhelp.microfocus.com/leanft/en/14.03/HelpCenter/Content/Licenses/LFTLic_LicenseFAQ.htm#hp-minitoc-item-8