Missed calls or messages not showing

[Lawrence557]

I have transferred from an a53 to an a55 mobile phone in the last couple of days. I am not receiving any notifications at the top left of the screen denoting a missed call, voicemail etc. I have gone to the phone app from settings and the allow notification icon is already shaded to accepted but it is shaded so it cannot be adjusted. On one of the 'solutions' ive seen it shows that if this button is turned on it would give options for missed calls or voiced mails to be enabled. I have also tried rebooting.

Can anyone suggest a solution?