Let me guess... you plugged the RJ-45 type plug from the 1747-PIC into the Ethernet port of the SLC-5/05.
Although the plug fits, Ethernet and DH485 are totally different and incompatible.
Let's take a step backwards and just use an RS-232 cable to connect to the SLC-5/05. Get a 1747-CP3 cable, or an ordinary RS232 cable with a "null modem" adapter attached.
Make sure the 1747-PIC driver has been deleted from RSLinx. In fact, you may wish to reboot your PC to be sure.
Now create an "RS-232 DF1 Full Duplex" driver in RSLinx. Use the Autoconfig button.
If that works, and you can go online using RSLogix 500 software, we can move to the next step of verifying your PC's TCP/IP configuration, the SLC-5/05's TCP/IP configuration, and the configuration of the RSLinx Ethernet driver.