Shares of the Phoenix company at last check were up 11% to $19.78.
"Due to covid-19 audience-size restrictions at Arizona's major venues, we have made the decision to reschedule an in-person Nikola World until we can bring the Nikola community together safely," Nikola said in a statement.
The company maintained in a statement that it "remains committed to achieving" a set of milestones to develop its commercial truck.
"Nikola expects the first batch of five prototypes of the Nikola Tre, a 100% battery-electric truck, will be substantially completed at our joint venture facility in Ulm, Germany, in the next few weeks," the company said.
"We remain confident in our ability to begin production of the Tre and make it available to customers starting in the fourth quarter of 2021."
Nikola also said it continues to make progress developing its one-million square-foot manufacturing facility in Coolidge, Ariz., which is scheduled to be completed by mid-2023.
The company has been beset by a series of problems, including allegations by Hindenburg Research that have sparked an investigation by the Securities and Exchange Commission and the Department of Justice; a share-price drop, and the resignation of its founder and former executive chairman, Trevor Milton.
In addition, Nikola's $2 billion deal with General Motors (GM) - Get Report that was slated to close Wednesday stalled after allegations of fraud and sexual abuse surfaced against Milton, CNBC reported.
Two women filed sexual-assault claims with Utah authorities against Milton. Both allegations were more than 15 years old but involve a cousin and an office assistant when both were 15.
Milton’s cousin, Aubrey Ferrin Smith, said he assaulted her in 1999 when he was 17 while the other woman says she was assaulted in 2004 when he was 22, CNBC said.
Smith's complaint was filed with the Unified Police Department of Greater Salt Lake in Utah on Saturday, CNN reported.
“Mr. Milton strongly denies these false allegations," a spokesperson said in an email. "At no point in his life has Mr. Milton ever engaged in any inappropriate physical contact with anyone.”
"Our transaction with Nikola has not closed," GM spokeswoman Juli Huston-Rough said in a statement to Reuters. "We are continuing our discussions with Nikola and will provide further updates when appropriate or required."
Nikola told TheStreet that it "continues to work with GM towards a closing."
The alliance, unveiled Sept. 8, included plans for GM to receive an 11% stake in Nikola then worth about $2 billion and payments up to $700 million for building the company's Badger pickup.
GM agreed to supply Nikola with electric batteries, a chassis architecture and a factory to build the Badger pickup, as well as GM's fuel cell system for Nikola's planned heavy trucks.