spindle doesn’t work

Using LINIXCNC 2.9.2 on Debian 12 in combination with a Mesa card 7i76e. The wiring is like thisMesa    <=>        VFD
Dir +                      +12V
Dir -                       REV
En +                       +12V
En -                        nc
nc
SPI +                      +10V
SPI OP                 AVI
SPI -                      COMI setup in the  INI file MAX_OUTPUT = 20000 which should correspond to 20000 rpm of my spindle specification. In the HAL file I setupnet spindle-cw                 =>  hm2_7i76e.0.7i76.0.0.spindir
net spindle-enable             =>  hm2_7i76e.0.7i76.0.0.spinena
net spindle-vel-cmd-rpm        =>  hm2_7i76e.0.7i76.0.0.spinoutsetp hm2_7i76e.0.7i76.0.0.spinout-scalemax [SPINDLE_0]MAX_OUTPUT I’m lost in what the issue is.
Any hints are welcome

Try connecting the mesa 'En-' to VFD 'FWD' and see if you can get the spindle to run in forward direction.

[edit]
Also, you need to uncomment this line in your hal:#net spindle-enable <= spindle.0.on

I made the change you advised, but no success.

Use the 'Show HAL Configuration' to verify that

'hm2_7i76e.0.7i76.0.0.spinena' is TRUE
and
'hm2_7i76e.0.7i76.0.0.spinout' is set

If that is ok then check if you actually have a voltage arriving at VFD 'AVI'.
Also check the VFD parameter settings to allow the spindle speed to be set by analog voltage input 'AVI'
If you have a potentiometer handy then you can connect that to the VFD analog input and see if you can change the spindle speed by manipulating the VFD inputs manually.

I made a simple test. Removing all wires from Mesa to VFD and making a short on AVI <=> +10V as well FWD <=> +12V. If I'm right the spindle should start right after I power the setup. But the spindle didn't start. Is my understanding correct that the VFD is broken?

and making a short on AVI <=> +10V as well FWD <=> +12V.

Since I see no other enabling input on the image of your VFD it is most likely a parameter setting issue in the VFD itself. My suggestion would be to have a look in the VFD manual. Usually there are parameters that need to be set to select the function of the analog voltage input.

I do have a panel where I can switch between manual and automatic. Was keeping it always in automatic mode.
Unfortunately, I've no documentation from this VFD.

I add another short between COM <=> REV and now the spindle starts rotating going to the maximum speed. Not bad, now I will return to the Mesa card wiring but now keep COM <=> REV.

So that would indicate that the digital inputs need to be connected to COM rather than +12V.

I that case you can try to connect FWD to En+ and COM to En-.

If you need to reverse the spindle then you will need an extra relay that at rest connects En+ to FWD and when energized connects En+ to REV. The relay coil is driven by DIR-.