I can only guess because I don’t know what exactly you have done so far.
It is not enough to “install” the EGroupware container. EGroupware is installed via docker-compose. This means that several containers are downloaded and configured.
That’s why the link to the documentation once again:
You should be able to run EGroupware on a QNAP NAS. However, we do not have a QNAP NAS ourselves and the standard installation provides for an installation on a system with an operating system.
Perhaps @svenp1 can help you further.
However, you must describe exactly what you have done. Without that it will be difficult.