WebAUGUSTUS retrieves large files from a public web link.
This web link points directly to the file, e.g.
https://ftp.ncbi.nlm.nih.gov/genomes/al ... mic.fna.gz
http://bioinf.uni-greifswald.de/webaugu ... es/LG16.fa
When putting this links into a browser, you will either
asked to download this files (like in the first example, as it is quite pointless to show a zipped file in the browser)
the browser shows you the file content and nothing but the content.
In contrast, if you put links to Google drive, Dropbox, BOX, ... into your browser,
you will see a webpage (sometimes with the file content embedded in this page) with a download button somewhere.
And only after you have pressed this button, the download will start.
WebAUGUSTUS don't "see" this download button and can't start the download.
For this reason WebAUGUSTUS don't support links to BOX, Google drive, Dropbox, ...
Maybe you can ask your administrator for a way to provide a web link.
If your genome file contains multiple fasta entries (e.g. one for each chromosome), you could split your fasta file into multiple files, each meeting the size limit of WebAUGUSTUS.
Please ask firstname.lastname@example.org
if you have a file that is larger than the allowed limit and there is no possibility to create a download link.