Agency - 404

Hi, I´m using Agency. Since some days I can't open the website. I get the message "Not Found - The requested URL was not found on this server." I can't open the front- and backend.
The Support of the hoster Strato say, maybe there is any plugin, who make the problem. I´m using only Joomla and Agency standard plugins, no other.
Is it possible, that one of the plugins is the reason for that. ... www.bogensport-schapdetten.de

Hello,
It could be a Domain setting!!!
But without Provider access I dont know what it is.
What have you done at least?

I had did an Joomla upgrade to 3.9.19.
After that the website runs well.
Some ours later I got the 404-Page.

The Strato-support said, the reason could be an extern plugin.
That was my important question here, if there is any plugin who make trouble (I use only the Agency plugins).
Today the strato-support has open a ticket and I will see, what the will answer.