Flask: 404 not found, routes to /register.html instead of just /register, can't find the issue

Beginner-ish flask user here, and i can’t find where i went wrong.
i am routed to (/register.html) instead of (/register) so i know it’s a blunder i made somewhere but everything looks alright to me, a pair of fresh eyes help me out.

Adding this because stackoverflow thinks my question is mostly code and wants me to add more details but i think my question is clear enough so please ignore this part.

@app.route("/register", methods=["POST", "GET"])
def register():
    # User reached route via POST (as by submitting a form via POST)
    if request.method == "POST":

        # Get username and password from form
        username_submitted = request.form.get("username")
        password_submitted = request.form.get("pasword")

        # Query database for user
        user = users.query.filter_by(username=username_submitted).first()

        # Ensure a username was submitted 
        if not username_submitted or password_submitted:
            flash("must provide username and password", category="error")
            return redirect("/register")

        # Ensure the username doesn't exist 
        elif len(user) != 0:
            flash("username alredy exists", category="error")
            return redirect("/register")
        
        else:
            # Hash password
            hash = generate_password_hash(password_submitted)

            # Insert new user into database
            new_user = users(username=username_submitted, password=hash)

            try:
                db.session.add(new_user)
                db.session.commit()
                # Redirect user to homepage
                return redirect("/")
            except:
                return "error signing you up"

    # User reached route via GET (as by clicking a link or redirect) 
    else:
        return render_template("register.html")

Here’s my register form:

{% extends 'layout.html' %} 

{% block title %} 
Sign up 
{% endblock %} 

{% block main %}

<form action="/register" method="post">

  <div class="form-container">

    <div class="form">
      <div class="username">
        <input type="text" name="username" placeholder="Username" id="username" autofocus/>
      </div>

      <div class="password">
        <input type="password" name="password" placeholder="Password" id="password"/>
      </div>
    </div>

    <input type="submit" name="register" id="register" class="btn" value="Sign up"/>
    
  </div>

</form>

{% endblock %}