Dataguard is not applying archive log files to the physical standby database

This is reported in the alert log:

Media Recovery Log /uB01/apps/oracle/product/11.2.0/dbs/archDLP01P_arch748005829_1_98503.arc
RFS[1]: No standby redo logfiles available for thread 1
RFS[1]: Opened log for thread 1 sequence 98504 dbid -1544167611 branch 748005829
Media Recovery Waiting for thread 1 sequence 98504 (in transit)

But standby redo log files are available:

rwxr-x---    2 oracle   dba             256 Nov  1 09:53 redologfiles
drwxr-x---    3 oracle   dba             256 Nov  1 09:53 ..
-rw-r-----    1 oracle   dba       209715712 Dec  7 20:45 redo01.log
-rw-r-----    1 oracle   dba       209715712 Dec  7 20:45 redo02.log
-rw-r-----    1 oracle   dba       209715712 Dec  7 20:45 redo03.log
-rw-r-----    1 oracle   dba       209715712 Dec  7 20:45 redo04.log
drwxr-x---    3 oracle   dba            4096 Dec  7 20:45 .
-rw-r-----    1 oracle   dba       209715712 Dec  7 20:45 redo05.log
-rw-r-----    1 oracle   dba       209715712 Dec  7 21:48 stby_redo02.log