Definitely join Twitter...I get most of my reads from posting on Twitter. I've pretty much given up on Tumblr, and dont get much response from Facebook; I think my IG is starting to pick up.
Also...be patient. Views arent going to blow up over a short period of time- especially if you've taken a lengthy break even before the story started to go anywhere. You have to "reintroduce" the readers that you had to you again, and that could take a long minute...just keep plugging away at updating the comic & tell people about your comic on social media(Facebook, Twitter, Insta, Tumblr, whatever else you have- I dont know; new social media sites spring up almost every day).