Print format - jinja extends/include statements

is it possible to use the Jinja {% extends … %} or {% include … %} statements in print formats? With the aim to have common parts of print formats on one place.

I tried the {% include “/files/header.html” %} but got message

Something went wrong
Server Error: Please check your server logs or contact tech support.

Best I would like to use {% extends “/files/my-letter-format-base.html” %} …

Where can I check the server logs? I am using the hosted solution on erpnext cloud.