Deploy application via business essential

Hi,

Does anyone have experience with the Business Essential application regarding pushing custom pkg?

I am trying to push for example Firefox pkg: https://ftp.mozilla.org/pub/firefox/releases/119.0.1/mac/en-US/Firefox%20119.0.1.pkg

I am unable to on freshly installed Sonoma, it is just spinning on installation:

First, I tried my custom app, which is a simple bash command "touch /Users/Shared/test" (compiled with Packages http://s.sudre.free.fr/Software/Packages/about.html) and I am getting an error:

App. is signed with my certificate which I distribute via ABM (apple business management).

I also tried couple a of times with support and they saw that there was something not ok (very straightforward process - Intro to deploying packages in Apple Business Essentials - Apple Support (LB) ) and they requested 3rd level of support which I need to pay ±600$, which is fine IF the issue is on my side, but I confirm that all is fine with the process on my side and they saw it. I asked about a refund in case it is something on their side, but they do not do that, so I am not willing to give them that money for a service which i already paid.

If someone has a valid package that is working on your side to give me the URL to confirm that there is a problem on my side or to cancel ABM subscription and to find another vendor for MDM solution.

Thank you