"RMAN-06026: some targets not found - aborting restore" kept occurring in restore

  Hello DBA group:

Any RMAN expert?  I've done multiple round of similar backup/restore between my 2 servers; db_name kept the same.  However, today it failed with "RMAN-06026: some targets not found - aborting restore".

source & target server OS structures are different. I use rman to backup, restore(after copy backuppieces across), and recover to open database.

(1). Source DB backup command [Danni: level 0 is same with option of 'level 0' substitude the 'level 1'.]

run {
allocate channel cd1 type disk;
allocate channel cd2 type disk;
set limit channel cd1 kbytes 2097150;
set limit channel cd2 kbytes 2097150;
sql "alter system checkpoint";
backup format '/orabackup2/SID/RMAN/SCRMPRD_%T_%s_%U_bak'