I have been doing lots a research and although I did not orginally opt-in for the Symbol airdrop from my understanding you can still do this up to 6 years after.
However, everytime I try to click on the " Symbol Opt In" section on the latest Nem Wallet 2.5.1 I just get the following message:
“Opt In has finished, please update your wallet to get the latest details”
Can anyone help as to what I need to do to receive my symbol coin or are they lost forever?
Opt-in is already closed.
If you held at snapshot and you did not optin you have wait post launch optin which will start in a few weeks.
Ok great thanks for the information I will try again in a few weeks, do we have an actual date or do I just need to keep checking back?
There is no date yet. But you will have 6 years so I doubt you will miss it.
You can check next month or just follow Twitter/Forum announcements.
Can’t, snapshot is already taken
does it mean that if I have hodl xem on the official wallet and did not have time to distribute, then I will receive xym ? can i spend xem now?
If you held at snapshot date (12th March 04:26:34 UTC) and you did not optin then you will be able to claim post-launch. Just make sure you did not lose access to your wallet and leave there 1 XEM to cover post launch claim transaction fees.
I am happy when possible to post-launch optin, It was not possible to do before because I am sick 
I followed a lot of the work by NEM foundation teams in 2020 and I read that the teams has changed, but its look positive. I am happy that Symbol is live!