Unable to enter in Programming mode (AT_Studio)

Question

I've a board with the SAML21E17B uC, when I want to connect/ program it using JLink(edu) and Atmel Studio I get and error message, that the IDE is unable to enter the programming mode

enter image description here

any idea what's the problem and how may I solve it ?

UPDATE

after Wossname answer I've resoldered the uC and double chekced the board, and could find and shortcut, and I still can get an access to the board , here's the part of schematic where the programmer is connected, maybe I've made a mistake here :

enter image description here

and yes I've place the capacitor and the induktivity near to uC as mentioned in the datasheet. And I've also set the programmer frequency to 32khz

• user98663: I've edited item 2 in my answer, that might help.

Answer 1

In most cases it is one of the following problems:

1. Clock speed is set too high in the IDE. The microcontroller you are attempting to communicate with is running at a lower clock frequency and cannot keep up. Set the IDE's clock rate to the lowest setting and try again.
2. There may be a wiring fault with the product you are connecting to. This is very common in hobby projects as opposed to manufactured products. Done it myself more times than I can remember :) Check that you have a pull-up resistor (4.7k is about right) between your nRESET pin and VCC, as that is a common omission.
3. There may be a firmware incompatibility on the programming tool you are using. Your programming tool may have older firmware than the IDE can use. Atmel's IDE will usually attempt to update the tool's firmware for you.
4. The computer may have the wrong hardware driver installed for your programming tool or has misidentified the tool. Uninstall the tool and attempt to reinstall using the latest drivers from the manufacturer.

• Engine: in the datasheet they didn't mentioned that, page 1221 atmel.com/Images/Atmel-42385-SAM-L21-Datasheet.pdf
• user98663: Atmel's chips often have internal pull-ups and they usually say that external discrete ones are optional, but in certain modes (with differen fuse options) it is possible for these to be disabled. I always use an external pull-up anyway, it's just easiest.
• Engine: @wossaname I've soldered a new board ( Reset without Pullup) and now I can read the device ID. clock Speed 4 Mhz as suggested from Segger . So yes it'S the 2nd point