Probably stripped (it is rather soft cast aluminum). Use a helicoil (need tap and a helicoil). Then you will be able to fix the threads and use the bolt again. The procedure is quite simple and the helicoil is available at any number of suppliers.

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Jovan

'84 (11/83) 190D 2.2 5-Speed; Silver/Blue; Motor No. 00354, 402k mi (340+kmi mine)

'89 Porsche 911 Turbo Coupe; Black/Black; 53kmi
'05 BMW 530i 6-Speed; 302kmi
'19 Range Rover; 30kmi