Due to an issue in PLAXIS 2D 2010 Output in the extrapolation from interfaces to plates, some nodal excess pore pressure values in interfaces and plates could be shown as zero-values. However, the excess pore pressures in the stress points are calculated correctly by the kernel. This issue only affects the post-processing in some of the nodal values: it is only an Output / display issue, the calculation itself is correct.
This has been fixed since PLAXIS 2D 2011.00