RCA 25403RE3 Corded Phone "error message line inhibited" Questions

...error message says that it is inhibited. My line 1 in-use button changes from red to greenish and intermittantly says that it is in use. I cannot transfer to this line or speakerphone this line and ...

...message saying " Error: inhibited ". Would you plaese help fix my problem. Thanks for your support in advance. Tom Hansem Travel Tom, I had the "error: inhibited" problem with my RCA 4-line ...