LTM is not Logging

Maybe there is a problem with your filesystem or the permissions on the /var/log/ltm file. What do they look like now? Can you give an output of the command

ls -ld /var/log/ltm

Can you try to add some text to the file yourself?

 echo test >> /var/log/ltm
 cat /var/log/ltm

You can also add an logging iRule to one of your virtual servers. For example:

when CLIENT_ACCEPTED {
    log local0. "Write this line to /var/log/ltm"
}

And check if the /var/log partition is mounted in read/write (rw) mode:

[root@nielsvs-bigip:Active:Standalone] log  mount  | grep log
/dev/mapper/vg--db--sda-dat.log.1 on /var/log type ext3 (rw,noatime)
[root@nielsvs-bigip:Active:Standalone] log