Admin,
Thank you for your help. When we checked our settings, they were the same as your screenshot. After some further digging, we found that there was a feature code enabled *55 to disable intercom. Our extensions were 5500-5599. When we disabled the *55 feature code, it worked.

I am having an issue with transferring calls to voicemail using FOP2. We are using 4 digit extensions (5558 for example) but when I go to transfer to voicemail, it says "The person at extension 58 is I'm sorry. That is not a valid extension." and then it hangs up. Any assistance with getting this fixed would be appreciated.