Phone Setup and Call Monitoring

I have a FreePBX 13 system using Digium IP Phones. On the sidecar only the first 35 users have the little man icon. We realized that when someone is on the phone only the first 35 will provide you an indication that the person is on the phone. User 36 and up don’t give any indication of phone usage. How can this be fixed where “all” users phones are monitored and give an indicator?
Thanks

It may be a hard limit imposed by the phone hardware. Your first task is to determine how many BLF subscriptions the phone supports.

Igaetz, thanks for replying. I found that the Digium D70’s firmware limits the first 40 BLF’s. Why I’m only getting 35 is still a question. I also found that my phones are way behind on their firmware upgrades. My question here is do I have to step through each upgrade one at a time or can I go right to the latest one? Also, can I just do my phone for testing without effecting the rest of the phones?
Thanks