Please delete your last response and again share the login details by making the reply as private. As this is a public forum so anyone see your website credentials. If you make it private then only we can see and use it.
I logged in to your website’s admin panel and I noticed that you have installed many plugins on your website. I suggest please try disabling all the plugins at once and then enabling them one by one to check what is causing this trouble. If this does not solve the issue, please try switching the website’s theme.
Please let me know if this resolves the issue or not.
I already did what you suggested before I contacted you. Also the theme is a theme I use already on other web sites which have your plugin on, with no problems.
Without ANY plugins active and with three pages refreshes your plugin does not prompt for new release upgrade. The none pro version is already on 3.1.24