Can't add Baikal calendar in Roundcube 1.6.11

[GCPSoft]

Hi,
I've been using Roundcube 1.6.11 for a few days, and I am unable to add a Baikal CalDAV calendar to this plugin. I was able to add the calendar into Thunderbird, but I'm getting an error trying this implementation:

[09-Oct-2025 17:23:23 -0300]: <2de5449b> caldav_driver: Sabre\HTTP\ClientHttpException: Unauthorized in /srv/sites/webmail/vendor/sabre/dav/lib/DAV/Client.php:303
Stack trace:
#0 /srv/sites/webmail/vendor/sabre/dav/lib/DAV/Client.php(198): Sabre\DAV\Client->doPropFind()
#1 /srv/sites/webmail/plugins/calendar/drivers/caldav/caldav_client.php(363): Sabre\DAV\Client->propFind()
#2 /srv/sites/webmail/plugins/calendar/drivers/caldav/caldav_driver.php(2074): caldav_client->prop_find()
#3 /srv/sites/webmail/plugins/calendar/drivers/caldav/caldav_driver.php(345): caldav_driver->_autodiscover_calendars()
#4 /srv/sites/webmail/plugins/calendar/drivers/caldav/caldav_driver.php(246): caldav_driver->create_source()
#5 /srv/sites/webmail/plugins/calendar/calendar.php(933): caldav_driver->create_calendar()
#6 /srv/sites/webmail/program/lib/Roundcube/rcube_plugin_api.php(577): calendar->calendar_action()
#7 /srv/sites/webmail/program/include/rcmail.php(262): rcube_plugin_api->exec_action()
#8 /srv/sites/webmail/index.php(278): rcmail->action_handler()
#9 {main}

I've used the exact same credentials and URL to add the calendar in Thunderbird, of course. I've tested with https://calendar.server.local/dav.php/calendars//default/, and https://calendar.server.local/dav.php, but to no avail.
In the screen is showing "CalDAV source could not be added".

I'm using Apache 2.4.63 and PHP 8.1.

I'll be glad to share more information about this if it helps. Thank you.