HP 4700 DN jet direct issue

[MichaelH5]

My HP 4700dn printer has been working problem free for many years as a wired network printer on a fixed IP address. within a windows peer to peer network of dektop pcs with Draytek router and Draytek switches.

There had been no changes on the network but suddenly network printing stopped. USB printing worked fine. It appeared that the embedded jetdirect had stopped working. I tried everything I could think of ... checked the network cabling and though fine with tester even replaced with another known good cable; did a cold reset; removed the formatter board and removed and re seated the firmware and memory cards then replaced the formatter board; performed another cold reset. Manually re-entered the tcp/ip settings. I still got

Status I/O Card Not Ready ;

LAN ERROR - LOSS OF CARRIER

Suspecting a hardware failure I tried another formatter board but found that was faulty as would not go beyond the memory check or allow a cold reset. I could not get another formatter board so put a jetdirect network card in the EIO1 slot on the original formatter board.

I disabled the onboard Jet Direct in case of confusion. Manually set the EIO jetdirect card to manual TCP/IP with an address one up from the original. 

Configuration print out now said I/O Card Ready with all correct TCP/IP settings including gateway and DNS

However I still cannot connect to the printer across the network and I cannot even ping the ip address. The EIO 1 card mac and ip do not appear in the router ARP cache table.

I am at a loss of where to go next short of replacing the printer which for various reasons I would rather not do