First of all, download setup file and run it on one of the servers in your Sharepoint 2019 farm as Farm Administrator. Follow wizard steps.
Note
Alternatively, use WSP package to install the latest version.
After the package installation, go to Site collection features and re-activate (de-activate and activate again) Plumsail Forms feature:
Navigate to the a list and click Design Forms:
Download the latest App package:
Navigate to the app catalog: delete the existing package, upload the new one and deploy it globally (check Make this solution available to all sites in the organization):
Download and install the new editor desktop app:
Clear browser’s cache to make sure all changes have applied: