Im not sure why the steps I suggested wont work.. For instance, you said that
""I use the wizard to define it to the network, and all is ok until I power the printer down/up"" So you are able to get it on the network, until you power down yes?
So that tells me, you should be able to define the printer, put it on the network. And then immediately try the steps I suggested. Once a static IP is set via the steps I suggested, you can immediately power down the printer and test if my suggestion worked.
As far as being upset, maybe you didnt understand what I was suggesting, however by your own description of the situation my suggestion should be viable. And its worth at least attempting it.
And if that doesnt work, its not a choice of replacing the printer or router yet. As there are other steps that could be done, but its senseless to discuss those steps until weve tried the suggestion I made first.
For tech support to work, you have to invest into the process and whether or not you trust who you are working with, if you dont attempt the steps suggested tech support could never possibly work.
I hope to hear back from you when you have had a chance to test out my suggestion.
Senior Technician and Network Switching Systems Operator / Maintainer.