Stuck at 100 on brand new site

This is the second time within a few weeks where the plugin won’t import my exported file to a new site.

It goes to 100 then hangs for 30 seconds and then throws this error:

[Error] Failed to load resource: the server responded with a status of 503 (Service Unavailable) (admin-ajax.php, line 0)

[Error] Error: error
error (import.min.js:1592)
i (load-scripts.php:2:27368)
fireWith (load-scripts.php:2:28123)
x (load-scripts.php:4:22611)
c (load-scripts.php:4:26778)

Through other posts it’s suggested that bad internet is at fault for this error, but my internet is working just fine and i have upload/download speeds way above 150 mbit/s.