You're facing the "You have no valid license file" message still after you uploaded a valid license file on the Rich Forms Add-In Homepage on your SP 2013/2016?
This could be the issue:
Authentication realm is not configured with Farm ID. This is a prerequisite of our Add-Ins.
- Open developer dashboard of your browser (press F12 and navigate to Console tab)
- Navigate to the Add-In Homepage of Rich Forms (just click on "skybow Rich Forms" in Site Contents of your site you installed Rich Forms)
- Check what is logged in the console after Current Realm?
Bad example: Text sprealm is set instead of Farm ID in format like this: Current Realm:0xxxxxx1-5xx6-4xx1-axx7-3xxxxxxxxxx3
To solve this issue, the SPAuthenticationRealm configuration must be changed. Have a look at this articles: https://docs.microsoft.com/en-us/powershell/module/sharepoint-server/set-spauthenticationrealm; Where do I see the tenant/farm ID?
$c = Get-SPServiceContext -Site "https://yoursiteurl..."
Set-SPAuthenticationRealm -ServiceContext $c -Realm "0xxxxxx1-5xx6-4xx1-axx7-3xxxxxxxxxx3"
Check first what this configuration change takes effect in your environment!
After this change you have to reinstall the Add-In on the sites.