Feather Express m4 COM Port Issues

[twillis]

After weeks of working with a Feather Express M4 on my work laptop reading a SPI ADS1262 and printing a .CSV line for its reading without issues. Meaning the normal compile and upload works , with data on the serial monitor. Suddenly, the IDE no longer recognizes the COM port for the USB serial communications. If put into the bootloader mode with the double press of the reset button, it will program the the Feather. But any attempt to access the Device Com port fails. Sometimes with “busy” or “can’t access” messages. Even Putty can’ts open the port, even though the COM port appears in the Device Manager without issues. The IDE / Serial Monitor hangs until the Feather is unplugged. Just using “Blinky” works fine, but still needs the bootloader mode to program. Adding a Serial print to Blinky with a 2 second delay after .begin works OK. A while(!Serial) never executes a print. A second Feather was tried, same results. Switching to a brand new Dell XPS15 with a fresh install had same results. The purpose of this device is to provide a serial datastream from the ADC readings. I have been using the Arduino IDE and Adafruit devices for over a decade. without issues, Tried going back several versions of the SAMD board files with no change in behavior. I am at a lost as to the next step, except going back the the UNO.

[twillis]

Additional information. When doing an upload, stalls apparently waiting for COM3. Double click reset button for the bootloader, and the upload completes on COM4, then switches to COM3 with the following error message:

Arduino: 1.8.16 (Windows 10), Board: "Adafruit Feather M4 Express (SAMD51), Enabled, 120 MHz (standard), Small (-Os) (standard), 50 MHz (standard), Arduino, Off"
Sketch uses 24020 bytes (4%) of program storage space. Maximum is 507904 bytes.
Device : ATSAMD51x19
Version : v1.1 [Arduino:XYZ] May 17 2020 17:56:23
Address : 0x0
Pages : 1024
Page Size : 512 bytes
Total Size : 512KB
Planes : 1
Lock Regions : 32
Locked : none
Security : false
BOD : false
BOR : true
Write 25328 bytes to flash (50 pages)
[==============================] 100% (50/50 pages)
Done in 0.402 seconds
Verify 25328 bytes of flash
[==============================] 100% (50/50 pages)
Verify successful
Done in 0.159 seconds
processing.app.SerialException: Error opening serial port 'COM3'.
at processing.app.Serial.<init>(Serial.java:152)
at processing.app.Serial.<init>(Serial.java:82)
at processing.app.SerialMonitor$2.<init>(SerialMonitor.java:132)
at processing.app.SerialMonitor.open(SerialMonitor.java:132)
at processing.app.AbstractMonitor.resume(AbstractMonitor.java:132)
at processing.app.Editor.resumeOrCloseSerialMonitor(Editor.java:2126)
at processing.app.Editor.access$1300(Editor.java:116)
at processing.app.Editor$UploadHandler.run(Editor.java:2095)
at java.lang.Thread.run(Thread.java:748)
Caused by: jssc.SerialPortException: Port name - COM3; Method name - openPort(); Exception type - Port not found.
at jssc.SerialPort.openPort(SerialPort.java:167)
at processing.app.Serial.<init>(Serial.java:141)
... 8 more
Error opening serial port 'COM3'.

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Device manager shows COM3 working normally, but will not work with the Serial Monitor or Putty.

[twillis]

Per IT (Log4J) recommendations to install IDE 1.8.,19, installed the latest IDE 1.8.57 from the Microsoft App store. Uninstalled the original Arduino IDE app. First attempt with the original M4 failed to open its com port. Unplugged M4, used Device Manager to delete the port. Re-installed M4 enumerated at the same com port. Used reset button to put M4 into bootloader mode. This had been tried serveral times without sucess. This time, sucessfully programmed, serial port working with Serial Monitor. Repeated code re-load did not require the bootloader mode, working normally as before.