First the obvious:

Check your list to make sure it is finite in excel. If you don't limit
it when you create the list it will go past the maximum number of
lines/columns

That sharepoint will accept.

I usually highlight the lists  manually, LMB and scroll, it's a pain, but
simpler than typing the junk in.

DNS, always check DNS..

Uploading large excel  files to sp can be a pain, they can also timeout
if they are hefty.. Try loading up the initial files directly on the
server if possible and then add to them after that.

Permissions, if you are setup to load other files, word docs, create
lists etc, then excel should be no different.

Syntax.. Obviously check to make sure the name of your file does not
already exist in SP as it won't overwrite like it will with a word doc.

Check if you need http://www.website/ or simply www.website
or just website on LAN..
Yes, I have seen this error between two servers and in my case it was a
dns thing on the LAN.