But perhaps you are trying to set the x and z from within the locations list file rather than from the URL? In which case beware that if coordinates are specified on the URL they'll override the position provided by the locations list - so check the URL you're using isn't centering the map to 0, 0.
Is there anything else that could cause this? I noticed the link I got the Unique Code from looks a little different from yours. It shows "view" instead of "edit." I tried changing the permissions to anyone can edit, but it still has the word view in the link.
Thanks! Looks like it will be exactly what I wanted once I get it working
I think you have the Google Drive sharing permissions of your file set to "anyone with the link can view"
Instead, the sharing permissions need to be set to "anyone on the internet can find and view", which is also called Sharing "On - Public on the web".
I'm not entirely sure of the distinction Google is trying to make between "public on the web" vs "anyone with the link", but when I switch one of my files to "anyone with the link" then it exactly replicates the chain of redirects and eventual error I get when I try to use your file in a map.
Also, your "Future mob trap" entry probably won't show up as the line doesn't start with a known location type (I could suggest "Label", "PlayerStructure", or "PlayerMachine").
The distance the map can display ocean depends on the size of the oceanmask.png, the .png is 1250 × 1250 by default and each pixel represents 16 blocks, meaning it covers a Minecraft area of 20,000 × 20,000, or 10km in every direction from spawn.
The problem can be resolved with a bigger oceanmask.png, but I've not written anything to generate larger ocean maps from a seed - perhaps unleash the inner cartographer and draw the far oceans