I opened your archive in 2020R2 to inspect your model.

First observation, if you kill the contact between the dead-weight and the board, you don’t need to lift the dead-weight up by 50 mm, you can leave it at 0, but that might still be a challenge since the board will have deformed in the -Z direction due to the 50 kg weight. It would be better to fix the pilot node at its current X,Y,Z displacement and X,Y,Z rotation in step 10, then kill the contact in step 11.  But that is not the problem you are having, you are asking about gettting step 1 to solve.

Second observation, bonding the dead-weight to the board adds stiffness to the board. It would be more accurate to use Frictional Contact between the dead-weight and the board. That would allow the board to flex underneath the dead-weight.

Third observation, if you have a beam connection between the brackets and the board, a good simplification is to suppress or delete all the No Separation contacts between the board and the other corner components since the board is going to become concave from the dead-weight and will want to lift off those surfaces.  I did that in case that helped the solution to advance.

While solving, there is a warning to pay attention to:

 Range of element maximum matrix coefficients in global coordinates
 Maximum = 3.06829627E+09 at element 87302.                             
 Minimum = 4.994212815E-05 at element 110614.                           

 *** WARNING ***                         CP =      64.047   TIME= 10:51:55
Coefficient ratio exceeds 1.0e8 – Check results.  

The ratio is approx. 6e+13 which implies an ill conditioned system and those do not give accurate results.

Looking at the materials, I see where you have made a mistake. You have entered the Yield Strength as 50 Pa instead of 50 MPa.
When material property values are off by a factor of 1e6, that tends to cause problems.

I changed the Bonded Contact between the dead-weight and the board to Frictional. Checking Initial Contact Status showed a problem.

To correct this problem, I changed the Interface Treatment to Adjust to Touch.

I changed the Initial Substeps on Load Step 1 to be 100, but it hasn’t converged with larger values for Yield Strength.

I changed the dead-weight from Rigid to Flexible, that got rid of the first error.

Now it starts solving. Getting the resut of the steps to solve might be accomplished by smaller initial step sizes.