Try these steps first to narrow down the source of the issue:
- If you are using a cordless phone, disconnect all cordless phones from phone jacks. If you have a corded phone, try it in the same jack. Sometimes, cordless phones are more susceptible to interference.
- If you cannot check the connection with a corded phone, unplug the cordless phone from the power supply for at least 15 seconds and try again.
- If possible, try plugging the phone into a different jack.