Cannot Connect to Out Of The Box 1756-L72

Plan on installing a 1756-L72 to replace a 1756-L61 this coming weekend.
Installed 1756-L72 into 1756-A10 rack, connect using USB driver, and flashed the firmware to V19.01

Now reboot PC, reboot 1756-L72, now when I try to download project via USB, get Error 701-80042504 "Unable to open connection - All connections may be in use". PLC is empty and this is the only device USB is connected to. Using Rslinx V2.57

Knowledge database indicates CPU may have too many connections, or module has too many connections.

Anyone seen this ?

I don't have an ENBT at the moment to get online with the 1756-L72 PAC

Make sure you have the v19 EDS file for the 1756-L72 registered, by right-clicking in RSLinx Classic and selecting 'Upload EDS from device'.

Then do the standard delete Harmony.HRC and Harmony.RSH, and reboot.

I'm just guessing at this point; I haven't used the L72 or experienced this error.

Ken Roach said:

Make sure you have the v19 EDS file for the 1756-L72 registered, by right-clicking in RSLinx Classic and selecting 'Upload EDS from device'.

Then do the standard delete Harmony.HRC and Harmony.RSH, and reboot.

I'm just guessing at this point; I haven't used the L72 or experienced this error.

Click to expand...

Managed to source a 1756-EN2T. Used the USB cable, browsed through the EN2T via USB to the 1756-L72 via backplane and was able to download the project