Border opacity in css using rgba() not working

I am working on a simple login site template using html and css (no js yet) and for some reason when I use the border-color property in my css for the .main class and i use the rgba() function like this:
border-color: rgba(255, 255, 255, 0.5);
the rgb works but the alpha does not at all.

I tried doing this instead and i also removed the original line:
border: 60px solid rgba(255, 255, 255, 0.5);

I am using chrome version 108.

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-css -->

html {
  height: 100%;
  width: 100%;
  font-family: Arial, Helvetica, sans-serif;
  background-image: linear-gradient(red, lime);
}

.main {
  margin: 60px;
  border: 60px solid;
  border-color: rgba(255, 255, 255, 0.5) !important;
  /* Set border opacity */
  border-radius: 30px;
  background-color: rgba(255, 255, 255, 0.8);
}

.main input {
  border-radius: 10px;
  height: 30px;
  background-color: lightgray;
}

.main input:focus {
  background-color: white;
}

.main button {
  height: 30px;
  border-radius: 15px;
}

<!-- language: lang-html -->

<center>
  <div class="main">
    <h1>Login</h1>
    <p>Hello! To continue please log into our service:</p>
    <h2>Email</h2>
    <input type="email">
    <h2>Password</h2>
    <input type="password">
    <br>
    <br>
    <button type="button" onclick='alert("logging in...")'>Login</button>
  </div>
</center>

<!-- end snippet -->

You need to add background-clip: padding-box; to limit the background to padding area and not have it under your border-color:

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-css -->

html {
  height: 100%;
  width: 100%;
  font-family: Arial, Helvetica, sans-serif;
  background-image: linear-gradient(red, lime);
}

.main {
  margin: 60px;
  border: 60px solid;
  border-color: rgba(255, 255, 255, 0.5);
  /* Set border opacity */
  border-radius: 30px;
  background-color: rgba(255, 255, 255, 0.8);
  background-clip: padding-box
}

.main input {
  border-radius: 10px;
  height: 30px;
  background-color: lightgray;
}

.main input:focus {
  background-color: white;
}

.main button {
  height: 30px;
  border-radius: 15px;
}

<!-- language: lang-html -->

<div class="main">
    <h1>Login</h1>
    <p>Hello! To continue please log into our service:</p>
    <h2>Email</h2>
    <input type="email">
    <h2>Password</h2>
    <input type="password">
    <br>
    <br>
    <button type="button" onclick='alert("logging in...")'>Login</button>
  </div>

<!-- end snippet -->

I took a look and there's no issue.
You created two styles very similar and with 50% or more of opacity:

border-color: rgba(255, 255, 255, 0.5)
background-color: rgba(255, 255, 255, 0.8)

I suggest you to create a good contrast between the .main background and border.

In front-end, you will need to learn about design too. So, one of the videos I suggest you to learn how to manage colors is: https://youtu.be/Qj1FK8n7WgY?list=PLAiIx7LPQuH3FN2B2oBNiWhPCBC2NdqDe

I believe that a better contrast between the background and border, and an opacity below 50% will solve your problem.