Tesla sales fell 28% last month in 30 European countries even as the overall market for electric vehicles expanded sharply, according to the European Automobile Manufacturers’ Association. The poor showing comes after Tesla’s billionaire CEO had promised a “major rebound” was coming last month, adding to a recent buying frenzy among investors.

They were selling on Wednesday, pushing the prices down more than 4% in early afternoon trading.

Musk had said Tesla was sure to get a boost once the company was done retooling its factories to produce a new version of its biggest seller, the Model Y. But that was finished months ago, and the new models are widely available. Investors are now hoping that a cheaper Tesla expected to be out later year will help reverse the sales decline.

Overall, battery electric vehicle sales rose 25% in Europe compared to a year earlier. The market for EVs was particularly strong in Germany, where Musk has angered potential buyers by publicly supporting the far-right, anti-immigrant Alternative for Germany party in elections. Overall EV sales there leapt 45%.

China’s SAIC Motor was the big winner for the month with its European sales of EVs and other kinds of cars jumping 38%. That has allowed the company to leapfrog Tesla, which a year ago was selling more cars in the region.

SAIC sold 18,716 vehicles last month versus Tesla’s 8,729.

The sales drop for Tesla comes at a crucial time for the company as it launches a test run of its driverless ‘robotaxis’ service in Austin, Texas. Musk says that if goes well, he expects to introduce the service in several other cities in quick succession and have as many as a million of the automated cabs on roads by the end of the year.

Reviews so far have been mostly good, but the service is limited to a dozen or so cars and some passengers have circulated videos of problems during their rides, including one showing a robotaxi heading down a lane for opposing traffic.

Federal traffic safety regulators said Tuesday they were looking into the videos.