Wednesday before last (07-Aug to be precise), I received my Nano33 Sense BLE. I plugged it and ran two of basic exercises (that accompany the library - BLE tests) preceded by the obligatory default Blink exercise. Everything ran without any issue under IDE 1.8.9 (Ubuntu 19.04) while 4 other genuine UNO/MKR and 2 UNO compliant boards were also connected through the same USB 2.0 hub.
Subsequently, I disconnected the Nano33 to work on adding components with a breadboard. After completing this step I discovered that the Nano33 while displaying its presence to the IDE would not accept any code upload with the following message (even for the default Blink exercise):
No device found on ttyACM4 An error occurred while uploading the sketch
I have tried several combinations including making the Nano33 the sole board plugged to the desktop (the ACMn digit duly changes, of course) but to no avail. The tell tale sign is that the on-board LED blinks in SOS mode but only as 3 slightly long blinks followed by 3 short blinks and the cycle repeats itself.
Searching for answers, I stumbled upon an issue at ModemManager's forum (#127) that appeared identical to my experience. Unfortunately, I do not know what ModemManager has to do in my situation (BLE?). I did by-pass the USB hub and connected the Nano33 directly to one of USB 2.0 ports on the motherboard but that didn't work. I can lsusb with and without the Nano33 connected and see that there is an assignment for the Nano33 when connected. Presumably the IDE too collects similar information but is unable to upload the code owing to some mangled setting? The ModemManager service is no longer running and therefore I do not know how it could interfere.
I would appreciate some guidance on getting the Nano33 to accept code upload from the IDE. As you can understand by now, I am totally new at this of work. I have been trying, on and off intermittently to work on this issue but I do not know how to proceed owing to lack of any traction on my part. Your understanding is appreciated.