Failed to start with single argument --renew

[toslan]

Trying to run the script with single argument as help suggests:
./zimbra-auto-letsencrypt.sh --renew
I get
./zimbra-auto-letsencrypt.sh: line 104: source: --: invalid option
source: usage: source filename [arguments]
zimbra-auto-letsencrypt.sh[err]: Letsencrypt tool '' isn't executable file.