'Zoey 101' Star Matthew Underwood Pleads 'Not Guilty' After Hookah Lounge Bust

Former Nickelodeon star Matthew Underwood -- who played Logan Reese on "Zoey 101" -- has pled not guilty following his arrest last month ... when cops busted him outside his hookah lounge in Florida.

TMZ broke the story ... Underwood was arrested earlier this month outside his Cloud 9 hookah lounge in Port St. Lucie for violating his probation -- a misdemeanor in Florida. The lounge is co-owned by Underwood.

According to law enforcement, a warrant was issued for Underwood's arrest after his probation officer discovered Underwood had failed a drug test. The probation officer listed other violations as well, like failing to complete a substance abuse program.

Underwood is currently on probation stemming from his prior arrest in April ... when cops say he was in possession of a ton of weed.