Best thing to do first is to double check they are not misidentified.
Search for the IP address in Lansweeper.
If that comes up with nothing, you can do a test with devicetester.exe, which can be found in Program Files (x86)\Lansweeper\Actions on your Lansweeper server. Perform the test from your Lansweeper server to the printers, submit any relevant credentials.
Thats should provide you with more details regarding the ports that are open on the printers. To get the most information, SNMP will need to be enabled on the printers.