Gtranslate is a translation service, it works like a reverse proxy.
So WP armour often block Gtranslate’s server IP.
Gtranslate doesn’t want to give user their IP range, so we couldn’t add their IP to whitelist.
Even we could, it would whitelist spammer too.
Gtranslate uses X-GT-Viewer-IP for real visitor’s IP address.
Other things worth mention:
1, Only paid Gtranslate works like reverse proxy.
2, Gtranslate works in 3 modes: nl.domain.com/ domain.com/nl or nldomain.com
So you could not simply add a exception by checking whether Gtranslate plugin is activated.