From now on, you will need a monthly subscription to access the Reddit API within Infinity for Reddit and this is because Reddit has started charging for API access since July 1st, 2023. The subscription starts at $2.99 per month and all the features inside Infinity will be available at any tier. Thank you for your understanding.
More info here:
https://www.reddit.com/r/Infinity_For_Reddit/comments/147bhsg/the_future_of_infinity/