From WP Portfolio settings, when you click the button to import the templates, the process seems to be stuck sometimes. The synchronization of the template library does not work as the server could not complete the import process. At such times, follow the below steps to resolve the issue:
1) Go to the portfolio setting and add this &sync_type=ajax in the existing URL in the browser and hit Enter.
2) Then inspect Element in the browser for that frozen sync button and find the class is disabled and remove it and again hit Enter.
3) Now that the Sync Freeze button will be enabled back and the sync process will start to work as normal.
After enabling the import button you can simply reimport the template.
Note: Do not reload the page and keep that page open while importing the template.