Nas storage node is not mounting the tapes automatically

Do you have pending messages for tapes to be mounted on NAS?

Are your tapes properly labelled and in the correct pool?
What happen when you mount the tape manually.
Try perform a library reset or an inventory?

Well, that second is probably cause for first as well. Now you need to narrow it down...

Yes pending mounts are also there ...And its not mounting the tapes automatically..

Secondaly marking the tapes read-only and full

Can you confirm you have appendable or expired media available in the pool you wish to use? If not do you have blank media available and automedia management turned on, or does the pool you wish to use allow relabelling from other pools and any of the expired tapes in the library have relabel to other pools set on their pool configuration? If not then you will need to manually label the tapes for use.
However, the marking of the tapes read-only may be a problem but it is not clear what is happening here - is data being written there? if so how much data? what messages do you see in the logs when the tape is marked as full?

Just to clarify the last point, you say tape is marked read-only/full after a few usages; can you confirm the types of tape and amount written:

mminfo -q volume=volume -r volume,written,volflags,type,%used

- should give us some useful info...