Import and Export failing and returning no error message
I am not a developer, but I believe you are running into timing out issues and you may have to verify that the server PHP settings in “php.ini” are set high enough to allow enough time for very long-running scripts/SQL statements to complete so that you end up with the import results screen (what high enough is, I could not say). 

In addition to that, if a service such as CloudFlare is in place, those settings need to be set to longer than 3 minutes if possible - while the script will continue to run on the server, you won't be redirected to the import results screen if you get kicked out to an error screen. That said, you should be able to find the import error file using something like CPANEL to access the site file manager and for search for "sqlImport.errors". You may wish to open a support ticket with Siteground if you need any help with access.

If all else fails (e.g. like not being able to get your hands on a programmer fast enough to complete your import within a deadline), I have on more than one occasion resorted to breaking down a single import file to smaller ones (say 500 records in your case) to avoid the timing out altogether - incredibly frustrating, but at least my deadlines aren't missed!

Hope this helps!
Tamar