Christian Klien does not possess a current F1 super license.
The Austrian 27-year-old joined the new HRT team earlier this week as a test and reserve driver, and is scheduled to drive Karun Chandhok's F110 car in Friday morning practice in Spain.
But with less than 14 hours before that practice session kicks off, it emerges that Klien - a veteran of 48 grands prix and years as a test driver - does not possess the mandatory FIA document that would allow him to exit the Barcelona pitlane.
To the APA news agency, team boss Colin Kolles explained the apparent oversight.
"As long as the contract was not signed, we could not even ask for a super license," he said. "It was all very last minute."
Kolles said he was hopeful the situation will be resolved by Friday morning.