Solution
This error will occur when the MP500 cannot detect a proper 13.56 MHz NFC field.
When the card emulation channel is opening, the MP500 device is trying to adjust the level of the RF modulated signal picked up in order to obtain a constant signal at the receiver input. If the system fails to adjust the level, the error “ERR: Unable to adjust RF field threshold (error 614)” is returned.
First, make sure your connections to the antenna are correct. If using the dual PICC-PCD antenna, make sure that the antenna is connected before powering on the MP500. Then, make sure you can see the blue or green LED on the antenna is lit. If not, your HDMI connection may be faulty.
Make sure that the reader under test is polling with a decent field strength level.
Reminder: You can measure the reader’s field strength in the Test -> RF MEASUREMENT section of MPManager.
Ensure that the simulation antenna used is correctly connected with the MP500 and positioned on top of the reader.
The simulation antenna MUST be connected to the MP500 before powering it on.
If you have to start the card emulation script before the reader starts polling, check the timeout setting to open the card emulation channel and allow enough time for the polling sequence to start.
You can adjust the timeout in the “common properties” window on the right side. We recommend a command timeout of 10,000 ms for opening the card emulation channel.

It is also possible to adjust the global script timeout to 20,000 ms. You can do this by clicking on Settings > Script/Log and setting the Script Commands Timeout to 20,000 ms. Be sure to click “OK” to confirm the change.
NOTE: The global script timeout must be greater than any of the individual step timeouts.

Finally, make sure that the reader under test is polling with at least 5 ms between each reader command.