Attempts to upgrade broadband online failing due to “technical issues”

[PWel88]

Sky are offering upgrade options for my broadband (currently on supafast 80)  so I selected Full Fibre 300 and added to my basket, filled the answers to the other questions and it then comes up with the delivery screen to select date for engineer but then fails with "sorry we are having technical difficulties...unable to proceed with your order"

. Please try later."

I've been trying for a few days now without success.....I do note that it defaults to full fibre 500 and the cynic in me suggests that it might work  if I added that rather than 300!

if anyone has any suggestions that would be good, but suspect I'll have to call them.

 Thanks.

[caesarome]

@PWel88 

You will have to call them if the website keeps failing due to this error.