Dutch chipmaker Nexperia, whose supply chain was disrupted after the Dutch government took control of the company in September, appealed to its Chinese units in an open letter on Thursday to help restore normal production.

In the letter, Nexperia’s Dutch unit said it had made repeated attempts to reopen dialogue but had yet to receive any response from its Chinese subsidiaries.

Nexperia produces billions of simple but essential chips used in cars and other electronics, and recent shortages have strained automotive supply chains, causing production slowdowns and stoppages. The company manufactures most of its wafers in Hamburg, Germany, before shipping them to Dongguan, China for packaging and distribution to customers.