Analog phone dialing and connecting to Ring Central phone

We are in the process of rolling out RingCentral phones to numerous locations in a primary care healthcare organization. The site with our pharmacy is still on the legacy analog phone system and our remote pharmacy location in another town is on RingCentral, this location is co-located with a medical and dental clinic that share a number. (the pharmacy has it's own phone number). Whenever the primary pharmacy location uses their analog phone to call the remote pharmacy number, the message alerts that the call cannot be completed as dialed. If the staff use their cell phones, the call goes through just fine to that remote pharmacy number. What is going on with this and how can I correct the configuration, settings, or something?