Imessage doesn't deliver

Hey there,

I sent an imessage (blue) to bf's iPhone, the bar above was pushed through when sending the message but there were no under-text-notifications such as 'delivered' or 'not delivered'. And my bf couldn't receive any messages from me neither can he send any to me (all of them show not delivered)

It's not the network connection problem as I have a stable connection as well as his. His phone was on the whole day as well.

I realised that it started not showing 'deliver' under messages after I was sending a voice memo. I went out of wifi range with the iPod once it had been 'pushed' through, not showing it has delivered yet. Could it be a network transit traffic which causes messages sent after the voice memo to get stuck since the voice memo was never delivered?

I have tried:

Rebooting the device a few times

Switching imessage on and off

Resetting network settings

Creating a new apple ID

None of the above has helped.

Further suggestions to resolve this issue would be greatly appreciated.

Many thanks,

Sarena