Then problem lies here:
fNAME = Dir(fPATH & "Availability*.xlsx")           'get the first filename from the fPATH
This line of code tries to find a file called availability*.xlsx" in the fPATH folder. It puts that filename into the fNAME variable.

This line of code:
Do While Len(fNAME) > 0
...simply means, "only DO the following codes if there is a filename in the fNAME variable that is more then 0 characters long.

It appears the fPATH is declared inaccurately (folder not there, spelled slightly differently, you forgot the final \ in the string...) or there is NO file in that folder that matches that wild card string.