Allow me to suggest a work-around that will let you get up and running immediately.
I also just recently switched from 1Password to Enpass and had this exact problem, but I found an easy work-around that doesn't require anything more than a 1PF and Enpass and access to the Finder.
Save the content to import from 1Password as a 1PF file and make note of the location in the Finder.
Create a new empty folder somewhere on your Mac. Call it whatever you want. This is where the files to import into Enpass will go.
Keep the folder you just created open in a separate window or tab and in a different window navigate to the 1PF file in the Finder.
Right click on the 1PF file and select "Show Package Contents". This will open the 1PF file (which is really just a special kind of folder).
Do a "Select All" of the files and folders you see in this package content window (⌘A).
Drag and drop the content you just selected into the folder you just created in Step 2.
Fire up Enpass and start the import process. Select 1Password and the 1PF file format as the import options.
When you are asked to select the folder in which the 1PF file exists, instead select the folder that you created in Step 2 above.
Enpass will now find the content to import from 1Password and import all of it.
I did these steps myself and I was able to import everything.
I'm not sure why Enpass doesn't see or work with the actual packaged 1PF file, but I suspect it might be because very early versions of 1Password a long time ago used to export content into a folder instead of a packaged 1PF file?
In any case, until Enpass fixes this, the steps listed above will let you get to work with Enpass.