If you see this error message (see screenshot below), it means that your current Facebook page role does not have the ability to create ads.
(Note: You can check what your current role is by clicking Settings on top of the Facebook page, then Page Roles from the left navigation.)
To be able to create ads, you need to reach out to one of the page admins. Take note that only a Facebook page admin can assign and change roles. See this article
Ask the page admin that your page role be changed to Advertiser. That way, you can create ads, promotions or boosted posts.
For your information :
Aside from the Advertiser role, here are other page roles that also have the ability to create ads, promotions or boosted posts:
For more information on these roles, visit this page.
To request access to a page in Business Manager (if, for example, you run an agency and will run ads on a client’s behalf), follow these steps:
1 - Head over to Business Settings in Business Manager: https://business.facebook.com/settings
2 - On the left navigation, below Accounts, select Pages.
3 - Next, click +Add. Then select the option Request Access to a Page.
4 - You will be asked to enter the page’s name or URL. After you enter it, choose the role that you need on the page. In this case, select “Page advertiser.”
5 - Click Request Access.
How to get your support tickets resolved faster
Statistics have shown us that the more you tell us when you report an issue, the faster we solve that ticket. So...
1 - If you have screengrabs, please include them. A picture is worth a thousand words.
2 - If you have recorded a video showing the issue you're having, please include that as well. A video is worth a million words.
We recommend a free service called Loom for creating these videos. (this is a link to https://www.useloom.com/)
3 - To speed up ticket resolution, follow these useful tips How to Write the Perfect Support Ticket (That Gets Results Fast)