Hi Katarina NYSTRÖM,
We do not currently provide support for Azure DevOps in this forum. Please continue to use their official support page for assistance.
But to get you started, Wiki entries are stored in a repo and will inherit permissions by default. Go to the wiki and then click the three dots to get to the security and ensure you have permissions to edit the content.
Please click Accept Answer and upvote if the above was helpful. Please add a comment if anything is unclear.