Please check your “USB computer connection” settings screen first!
Check the "connect as" section, make sure that you do not use “Charge only”!
Make sure that you check this dialog first! And change the settings (best to MTP) before you read the rest of what I’ve written here. The dialog is a bit hard to find. Really double-check this! I read what you wrote, but it’s sometimes better to check twice.
If this did not work – other possible reasons (hopefully not in your case)
The “no messages part” worries me a bit. So if all the above really did not work, the usb connector could be damaged.
There is some info about usb here on the forum. I’m not an expert, but to me it looks like maybe the data ports (they are in the ‘middle’) of the usb connector became loose, while the pads for the power (on the “outside”) are still working.
But I can be wrong and it’s just a software issue, see above!
You could make sure by peeking inside the phone (are the pins of the connector on the board still okay?). Or by carefully cleaning the connector from the outside with a thin needle (lint, sand, etc.)
Only do this if you know the risks.
Please also wait for answers from the others before you do something, maybe they know more than I do. Maybe in the end contacting the support will be the better solution.
Update: This is how my FP1 looks like if connected (3.19 kernel):
[13426.291616] usb 1-8.3: new high-speed USB device number 6 using xhci_hcd
[13426.380887] usb 1-8.3: New USB device found, idVendor=0bb4, idProduct=0c02
[13426.380895] usb 1-8.3: New USB device strings: Mfr=2, Product=3, SerialNumber=4
[13426.380899] usb 1-8.3: Product: MT65xx Android Phone
[13426.380903] usb 1-8.3: Manufacturer: MediaTek
[13426.380906] usb 1-8.3: SerialNumber: XXXXXXXXX
Depeding on the mode (MTP or debugging) it should show up with usbview as
MTP
0bb4:2008 xxxxxx
or with usb debugging as
0bb4:0c02 xxxxxxx