Are you asking if this gives you a defence?
I cannot really give you good news.
The plain fact is that you are summonsed to court.
I realise that you are not to blame for the inability to send your licence to them but I'm afraid that there is an element of luck with things like this.
If you couldn't send your licence in then they couldn't add the points so the fixed penalty could not be accepted.
Therefore, they have summonsed to avoid time barring.
In those circumstances, you don't have too many options other than to plead guilty and mitigate on the basis that you tried to accept the fixed penalty but could not.
You might find a Bench that will just add three points and a fine of £85 plus the surcharge of £15 so you would be dealt with as though you had the fixed penalty anyway.
Can I clarify anything for you?