Matomo doesnt count all my users


hope i can find an answer to this question.

Im running a magazine, which has a few thousand visitors a day. We are having an external institition (its IVW in Germany, they count media stats) which has a pixel on our site as well which counts users. soooo

ill explain with the numbers from Monday. all other days have about the same ratio:

AWStats (a very basic stats system) counts: 5.539 Visits
IVW (the official media stats counting system in Germany): 5.517 Visits


Matomo: 3.901 Visits

We have put Matomo onto our server, without cookies. Its not getting handled by the CMP, therefore should load without any restrictions.

Hope anybody can show me the reason why Matomo only counts 70% of the users? All other days have about the same ratio.

All the best and thanks,