Mine was resolved recently.
Nationwide had made a mistake - IG hadn't cashed the cheque that was sent to them. They were able to cancel the cheque and restore funds in my ISA so I could transfer this elsewhere.
Throughout IG customer service had been a nightmare - repeatedly web chat promised to come back to me by the end of the day, but never did so. Putting the problem back to me to resolve. Refusal to escalate. On the phone they said they had just received the funds and will be credited to my account in 24 hours (untrue).
Knocked my confidence in IG enough to transfer elsewhere, which is a shame as the ISA product is perfect for me (flexible, £3, lowish fx), and there isn't really an equivalent elsewhere with these features.
I have a large spread bet position with them which I feel worried about now given what happens when there is a problem.
Good luck with yours!