Could be a lot of reasons.
Firstly no such thing as a standard RS232 comms cable, the DT80/800 need what is called a 'null modem' cable. That is pins 2/3 & 7/8 cross over between ends, pin 5 should be straight through. The connection is shown on page 214 of the DT80 manual.
Other basic thing is to ensure the definition of the connection in Delogger/ Detransfer software is correct for your PC and DT80 combo. Right COM port, baud rate settings etc.
Otherwise, can you connect with USB to at least know you don't have issues with passwords etc.
Could be a lot of reasons.
Firstly no such thing as a standard RS232 comms cable, the DT80/800 need what is called a 'null modem' cable. That is pins 2/3 & 7/8 cross over between ends, pin 5 should be straight through. The connection is shown on page 214 of the DT80 manual.
Other basic thing is to ensure the definition of the connection in Delogger/ Detransfer software is correct for your PC and DT80 combo. Right COM port, baud rate settings etc.
Otherwise, can you connect with USB to at least know you don't have issues with passwords etc.