I have a site https://www.prettywildseeds.co.uk/ which works fine on desktop and shows the pad lock but as soon as that site is opened on a mobile device then it doesn’t shows the padlock and says connection is insecure.
I am not sure how to check as to what is causing mixed content on mobile device only. Is there some tool or something that I can use to test the same ?
That means your mobile device is loading an http: version of the site rather than an https: (secure connection)
If your loading the page from a bookmark on your mobile have you checked to see if it is saved as the http: version? If so update your bookmark to the https: version.
I think you should also have a redirect on your server settings that would prevent that from happening. If it is not set up to redirect to the secure connection you need to address the problem there too.