Landline phone access to Zoom meeting stopped connecting

[RHosie57]

I'm in Australia.

A user who previously accessed Zoom meetings by landline phone (1-2 years) can now no longer connect.

Using the same phone which previously gave no problem, you can dial the number that connects to Zoom and  make a connection.  You receive the message, 'Welcome to Zoom', please enter your meeting ID.

When you start entering the numbers for the meeting ID on the phone keypad you get a message saying you have not entered any numbers and it disconnects. 

I tried the same numbers on my mobile phone and it connected fine.

Would anyone have any idea please why it suddenly stopped working, and what the solution is.

The landline phone is an older model Uniden wireless phone (which as noted previously worked fine).  I don't have the model number of the phone with me at present.

Thanks for your advice.