Answer:
The compression forces in cables or tension members can be displayed if the number of iterations was not sufficient for the calculation, and thus no convergence was achieved. You can set the number of iterations in the calculation parameters in the Global Calculation Parameters tab (see Image 01).
The maximum number of iterations is set to 100 by default. However, this does not mean that all iterations will be run. Depending on the structural system, the calculation often converges much earlier.
Also, check the settings for Reactivation of Failing Members. When selecting the "Assign reduced stiffness to failing members" option, small compressive forces may arise.
If this is not justifiable, select the "Failing members to be removed individually during successive iterations" option. However, you should pay attention to the sufficient maximum number of iterations (see above).