10:05 AM PT -- Authorities tell TMZ ... Gary Oliva is NOT actually missing. After we published our story earlier today, officials realized a clerical error had been made -- his current address had not been updated in the state's sex offender registry.

It's unclear when Oliva moved, but he's been checking in monthly ... most recently, on November 4. He is not out of compliance with parole conditions. He currently resides on the 1900 block of 29th Street in Denver, which authorities tell us is technically a "transient address."

Oliva had not been seen at his previous address for months ... 'cause he did not actually live there anymore ... and, again, did his due diligence with Denver authorities when he moved.

The convicted pedophile who claims he accidentally killed JonBenét Ramsey has gone "missing" ... TMZ has confirmed.

Gary Oliva has said for years ... he was in the Ramsey home in December 1996, when "I let her slip and her head bashed in half and I watched her die." Oliva wrote that to a high school friend in 2019.

When authorities were investigating the case, his name came up and they found hundreds of pictures of JonBenét.

Oliva had also confessed to other killings, but was never charged. He served an 8-year sentence for child pornography, but e's out and on parole until February 2027.

Denver authorities tell TMZ ... as a sex offender, Oliva is required to check in with the P.D., and it's his responsibility to check in with them. According to records from the Colorado Bureau of Investigation, Oliva has not checked in since February 2024 -- his location listed as the Silver Spur motel in East Colfax.

The Daily Mail has a police source who says Oliva checked in with them early this month and that means he is not out of compliance ... which we have not been able to confirm. However, State records do not reflect that -- although it is unclear how often those records are updated.

DM also reports -- he'd not been seen at the Silver Spur in months, hence "missing." According to public records ... Oliva has a history of failing to report as a sex offender and has multiple addresses listed on the CBI sex offender registry.

During a 2019 investigation into JonBenét's murder, Oliva was already locked up but eliminated as a suspect because his DNA did not match the evidence at the murder scene. But, recently, there have been significant questions about DNA testing back then.

The timing here is interesting, coinciding with the new Netflix doc, "Cold Case: Who Killed JonBenét Ramsey?" The doc raises the question as to why Oliva has been eliminated as a suspect ... even with unreliable DNA evidence.