I have added a lookup field in the form, but it is not appearing in the form through the web browser.
Welcome to Plumsail Community!
Please try to completely clear browser cache or open the form in incognito window.
If the field is still not displaying - make the screenshot of the errors in the browser console(F12).
What version of the app package are you using? You can check it in the SharePoint App Catalog. The latest version is 126.96.36.199
If you are using an outdated version of the app package, please update it. You can fin instructions here.