Out of curiosity could you check if you have the force ssl set to true? You can change this setting in /etc/passbolt/passbolt.php or /etc/passbolt/default.php I suggest changing it in the former.
In passbolt.php you need to add the following snippet in the passbolt section:
'ssl' => [
'force' => true,
],
or in default.php
'ssl' => [
'force' => filter_var(env('PASSBOLT_SSL_FORCE', true), FILTER_VALIDATE_BOOLEAN)
],