SPO2019 modern script editor query

Hi

I am a Librarian and we are exploring using SharePoint as a site for users to access resources. Please note l am learning SharePoint from scratch

I am attempting to embed a search box which enables access to our e-resources. The search box is provided by EBSCO.

When attempting this, the HTML code goes in fine using Modern Script Editor web part. However, when l enter any search terms into the box nothing happens. Usually it would execute the search and then provide results on the EBSCO page.

We did successfully insert a variant of the search box using Embed and an iframe but the rendering on mobile was poor along with zero scope to edit and customise the appearance of the search box.

My question is whether l am missing something in terms of permissions / site or page settings that would impede it working? Has anyone attempted to insert a HTML based search box into Script Editor?

Any advice would be welcome. I do have access to SharePoint Designer so could the code be inserted into the page via this instead?

Thanks

Alan