This happened to me for a late sale of a game last season, and they never turned up anywhere, and I lost out financially as they wouldnt let anyone else collect dupes.
Happened to me last season as well for City away. I put postal when ordering. I tried to give as long as possible for them to turn up, until I got in touch. Contacted on the Friday and they told me they were down for collect at Anfield. I never do that apart from cup finals. I could not get to the ground as I was in work, so asked to be put on the dupe list, as it was 1230 ko the next day. They told me where the collection point was at City.
Went to the collection point 90 mins before ko as advised - no dupes - my name was not there. This was man city ticket staff, but they had a lfc ticket office member there. They could not find me on the list, so they called Anfield ticket office. They got off the phone and advised me my tickets were at Anfield so they could not issue duplicates here. Luckily I had the email from LFC chat to show someone had told me I could collect dupes and even gave me directions to the city collection point.
It's not like I was going to get to Anfield and back in what was now probably about 70 mins, I asked can't they just rip the ones up at Anfield and re-issue? Went off for another call that took some time and eventually a mcfc ticket office member took me to another window to print them off. They were openly laughing at our ticket office as we went to the window. It was a shambles, took about 45 mins from when I got to the collection point. There were points when I genuinely thought they were not going to issue them.
I felt sorry for the person from our TO their as it was not really their fault. We have some really awful systems in place.