Like during the holidays or something? I used to be able to play but as I recall, I lost access when my membership ran out like 3 years ago

They used to occasionally open RSC back up to those new players who wanted to play, or people who lost access, but they said the last time they did that would be the final chance.

From Jagex's wiki:

 

Only two types of Members' accounts can play RuneScape Classic:

 

Members who logged in, at least once, during the 6 month period between 3rd August 2005 and 3rd February 2006

Members who logged in during one of the re-opening periods:

• 11th November 2009 through 25th November 2009
  
• 1st June 2010 through 24th June 2010
  
• 14th September 2011 through 28th September 2011

At this time, there are no plans to re-open RSC in the future though the game remains open to support the loyal players and to those new to the community alike. Though RSC is open only to qualifying accounts with active Membership, continuous subscription is not required to prevent loss to access rights. In the event of a lapse in subscription you will be unable to log in to RSC until you resubscribe.

 

From the sounds of it you should be able to play again if you are a subscribing member since you were able to before.

If you registered your account to classic anytime in one of the opening sessions after it has closed down for new players, you will still be able to play it when you get members again(Or, that's how it should work at least)

Hmm. I should be able to get in but I haven't tried since early after the closure.