Accidentally cancelled my Annual Plan for Adobe CC

Unfortunately no.  An account is either active or cancelled.  You can't change your mind after it's cancelled.  It's gone forever.

When you cancel a prepaid account it will stay active until the end of the period. You just need to take a new one then. 

It's, however, more tricky when stock is implicated. There you will lose accumulated assets. That should get a resolution from Adobe customer care. 

Hi @Team25103225bbfx,

They should be able to restore your account as per I see from staff responses on other similiar requests like the one mentioned below

https://community.adobe.com/t5/account-payment-plan-discussions/account-accidentally-cancelled/m-p/10177601#M26900

Please contact support and talk to a human instead of a bot. Login to your account and navigate to the URL below, it will open up a chat popup automatically, wait a while for it to open. Make sure that the browser has cookies enabled, and all script blockers are disabled.
https://helpx.adobe.com/contact.html?rghtup=autoOpen
Type AGENT to avoid bots and talk to a human.
Also, be mindful of answering anyone who sends you a private message. See the following for more information about scammers
https://tinyurl.com/y7cfrr7y
-Manan