Quote:
My web service uses http protocol ...
That's a likely culprit. Passing user credentials over an unsecured network protocol is an extremely bad idea, and is likely to be blocked.
Update your web service to use HTTPS instead. Depending on where and how it's hosted, you may even be able to use a free certificate from
Let's Encrypt[
^], so it won't cost you anything.
NB: If it's hosted with a company that won't let you use a free certificate, then you should take your business elsewhere.