Hello from France
I am currently experiencing the same problem.
I forced the update with with wxastronomy.php?force=1, and nothing makes, always the same error.
I deleted the cache file, checked the cache access rights but the file is not re-created.
I recreated the USNO-moondata.txt file by hand with access rights and still nothing. the file is still not updated!
My get-USNO-sunmoon.php file version is 3.01 - 20-Oct-2017.
I do not know what to do....
Any ideas?
Best regards,
Pierre