Bootstrap radio buttons inside my asp.net core mvc are shown as disabled

I have the following code inside my asp.net mvc core web application to show 2 radio buttons:-

<div class="form-group"><label class="control-label" style="font-weight:bold">@Model.SubmissionQuestion[i].Question</label><br/><div class="custom-control custom-radio"> <input type="radio" asp-for="@Model.SubmissionQuestionSubmission[i].Answer" value="true"  class="custom-control-input" /><label class="custom-control-label" style="color: #7e7e7e;font-size:14px;font-weight:bold">Yes</label></div><div class="custom-control custom-radio"><input type="radio" asp-for="@Model.SubmissionQuestionSubmission[i].Answer" value="false" class="custom-control-input"/><label class="custom-control-label" style="color: #7e7e7e;font-size:14px;font-weight:bold">No</label></div></div>

which will generates the following markup:-

<label class="control-label" style="font-weight:bold">Are you currently ...?</label><br><div class="custom-control custom-radio"> <input type="radio" value="true" class="custom-control-input" name="SubmissionQuestionSubmission[0].Answer" id="SubmissionQuestionSubmission_0d__Answer"><label class="custom-control-label" style="color: #7e7e7e;font-size:14px;font-weight:bold">Yes</label></div><div class="custom-control custom-radio"><input type="radio" value="false" class="custom-control-input" id="SubmissionQuestionSubmission_0__Answer" name="SubmissionQuestionSubmission[0].Answer"><label class="custom-control-label" style="color: #7e7e7e;font-size:14px;font-weight:bold">No</label></div>

but the radio button i got will not be select-able (as-if they are disabled),, any idea what is going on?

Thanks