Make sure you're following all the below steps to add a form to a page::
1. Open the Toolbox. In the Forms section, select and drag the Sitecore Form Wrapper rendering to the relevant placeholder.

[![enter image description here][1]][1]

2. After that, drag an Mvc Form to the Sitecore Forms Wrapper.

[![enter image description here][2]][2]

3. After dragging the Mvc Form onto the page, In the Select the Associated Content dialog box, select the form that you want to display on the page and click OK. The form is now displayed on the page.

4. In the Experience Editor, click Partial Design and click Metadata. In the SXA Toolbox, in the Forms category, drag and drop the Forms Scripts component before the closing /body tag of the page.


  [1]: https://i.sstatic.net/I80Iq.png
  [2]: https://i.sstatic.net/H9wyo.png