Error trying to download ERA5 data: Exception: Missing/incomplete configuration file: C:\Users\username/.cdsapirc
I had the same problem but have just found the solution after an hour or so of trawling through forums! The problem was that the code 'api.py' could not find the '.cdsapirc' file. The file type has to actually be 'CDSAPIRC' and not a 'txt' file. The icon for the file will then be displayed in your folder as blank and the name will be '.cdsapirc'. I found the solution on here: https://www.wikihow.com/Create-and-Delete-Files-and-Directories-from-Windows-Command-Prompt. I created the file using the following steps:


Navigate to 'C:\Users\username' (or you can just move it later). 
In Command Prompt, write 'type nul > .cdsapirc' and press Enter. 
Right-click the file and press 'Edit with Notepad++' (probably works with other programs).   
Paste the text that you already mentioned (key, etc). 
Save and close the document.  


Hope that works :)