thanks a lot in advance
If the slave image is empty, the coregistration failed. Please have a look at the InSAR Stack tool (View > Windows > Analysis > Radar > InSAR Stack) to check the number of remaining GCPs.
Usually, it is not possible to coregister SLC data from different looking directions as in your case.
Thank you very much for your reply. do different directions refer to rising or falling tracks？
yes, coregistration can only handle images which are both ascending or both descending.
An example is given here: INSAR / DINSAR - Perpendicular baseline calculation
A solution is provided here: Coregistration S1, empty images
Oh！！thank you for your enthusiastic help very much！