They removed port forwarding back in July

https://mullvad.net/en/blog/2023/5/29/removing-the-support-for-forwarded-ports/

I think it was something todo with CSAM hosting. It's shit but understandable to why they removed it

https://mullvad.net/en/blog/2023/4/20/mullvad-vpn-was-subject-to-a-search-warrant-customer-data-not-compromised/

https://mullvad.net/en/blog/2023/5/2/update-the-swedish-authorities-answered-our-protocol-request/