Trunk 2 switches with 10 Gb SPF+

I am trying to connect 2 switches with a 10Gb SPF+ module we just bought.

The 1st Switch of 2 switch ssack is the stack master, the 2nd switch is a stack member:

Switch Ports Model SW Version SW Image

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• 1 28 WS-C3750G-24TS-1U 12.2(50)SE5 C3750-IPBASE-M

  2 28 WS-C3750G-24TS-1U 12.2(50)SE5 C3750-IPBASE-M

Now I am trying to connect a 3rd switch from its SPF module to one of the 1st switch's (stack master) SPF module using this cable: https://www.fs.com/de-en/products/30862.html

3rd switch:

Cisco IOS Software, C2960X Software (C2960X-UNIVERSALK9-M), Version 15.2(7)E1, RELEASE SOFTWARE (fc4)

Both SPF modules are currently down (err-disabled)