Guacamole 1.3.0 / Labels not shown

[Davide Oliva]

 Hi all, dear fellows!
I'm experiencing a little trouble with Guacamole 1.3.0 installed on Debian
10.
Guacamole server is behind an Nginx reverse proxy.
Practically, labels (e.g. Username, Password, Login, etc.) are not showing
anymore replaced by placeholders like APP.NAME or {{getfieldheader() |
translate}}, but until yesterday all seemed to works smoothly.
Any suggestion to point me where look for an answer? Perhaps an update on
Guacamole server or Nginx could broke labels showing? It seems so strange
to me...
Thank you in advance for your help!
Davide

P.S. I hope my English is sufficiently understandable...