Mobile menu 404 error
 

Site: pbyc.de
PHP: 7.3.13
Msql: 5.7.25
Joomla: 3.9.24
Template: Eximium

The template has been running for years is excellent. Love it. Thank you.
When used on a mobile one menu link, this one
https://www.pbyc.de/?Itemid=118 which should show 4 menu items
goes to a 404, couldn't find page. All other mobile links seem to work fine.
Unfortunately that page is only viewable by registered club members and needs a login so I cannot show you.

Would appreciate a clue on what I might have done wrong as I am a hobby website maker for my club.
Thanks.

Are you sure your are posting in product assigned forum?: Yes

What is your CMS version?: Joomla 3.x

MySQL Version: 5.x

PHP version: N/A

Link to installation: pbyc.de

Have you edited any files? If yes tell us which ones.: No

Is this personal or client website?: Personal