妹纸真心提问，望大神看到回答

错误以及警告里边出现这个一般是哪里出了问题啊，怎么解决

DIFFERENTIAL STIFFNESS MATRIX IS COMPLETELY NULL.  THE EIGENPROBLEM CANNOT BE SOLVED.  IN A *BUCKLE ANALYSIS THE MOST LIKELY CAUSE IS THAT A NONZERO LOADING PATTERN WAS NOT SPECIFIED VIA *BOUNDARY, *CLOAD, *DLOAD, ETC,.  SEE Eigenvalue Buckling Prediction IN THE Abaqus/Standard USERS MANUAL

Abaqus/Standard Analysis exited with an error - Please see the  message file for possible error messages if the file exists.

Slave surface assembly__pickedset23_cns_ is a node-based surface used with surface to surface approach. In order to obtain improved stress accuracy with this approach, an element-based surface should be used instead.

For *tie pair (assembly__pickedset23_cns_-assembly__pickedsurf22), adjusted nodes with very small adjustments were not printed. Specify *preprint,model=yes for complete printout.

For *tie pair (assembly__pickedsurf25-assembly__pickedsurf24), adjusted nodes with very small adjustments were not printed. Specify *preprint,model=yes for complete printout.

The specified type of interaction cannot be created or resumed in this type of step. Contact pair definition will not written to the ODB.

There are 2 unconnected regions in the model.