newbie - simple import - what could be issue?

Hi, I have a provided Excel sheet from a shipping company, where i can export from my shipping software to their web portal for creating shipments. They provided an Excel template, but even their template with 2 shipping records will not always import, giving an error message (on the portal) of "file is empty." But yet, it did import at one point and i have no idea what the trick was. Not sure if it was from my laptop, desktop, saved as another version of Excel or what. Tried EVERYTHING all weekend. Are there any obvious things i can check? I'll try their tech support tomorrow, but being a Latin American company, it's hard to understand them fully. Tried that already, but will have to try again, just have packages piled up and with this being a new method, there are a lot of details delaying everything.

sample file is attached.

thanks for any help. MASSIVE IMPORTS.xls