Connect My Cloud drive remotely as a Windows credential?

I recently purchased a My Cloud drive, and set it up as a network drive on my home computer (on the same network) by adding it as a Windows Credential. I have port forwarded the device on port 80 and tried adding it as a Windows Credential the same way on a laptop connected to a different network. I entered its address as xx.xx.xxx.xx:80, but I can't get the drive to show up this way. I have double-checked that the port is open and that the IP is my external IP. Is it possible to connect to it this way despite being on a different network?

It won't work if you're using private IP addressing on your LAN. That's because private IP addresses can't be accessed as such over the Internet (this can be solved with proxy and NAT, we may get to that later). What are the first two octets in the device's IP address?
You tell me, then I'll tell you!
Thanks and HTH,
--Ed--

Wait, did you mean the router's external IP, or the drive's IP? The router's external IP starts with 71.74. As for the drive, I only know its internal IP starts with 192.164.

Then your router already has a proxy or NAT set up to make this device available over the Internet. The easy answer is not the correct one in this case. You might want to connect the driver maker's tech support (or check their FAQs and support postings) to see if this is a known problem (better still, if it is a known problem with a solution already available). Sorry to get your hopes up unnecessarily, but at least you don't have to set up a proxy (which can be tricky) or turn NAT on (not hard, but often takes rooting around in manuals).
Keep us posted on your resolution: you've got me curious now.
Thanks,
--Ed--

You might not be able to do it through File Explorer, but you'll probably be able to do it through a browser window. What diff does it make, as long as you can access your files?
Hope it works out for you!
--Ed--