HTML

how to enable button after checked

<input onclick="alert('thank you for agreeing to the terms and conditions')" type="submit" name="sendNewSms" class="inputButton" id="sendNewSms" value=" i agree to the terms and conditions " />

<input type="checkbox"  onchange="document.getElementById('sendNewSms').disabled = !this.checked;" />
<!--this will only work if u click the up arrow button on the right side--> 

Disable button if one of the checkboxes are not checked

const checkBoxes = document.querySelectorAll('input[type="checkbox"]');
const submitButton = document.getElementById('startusing-button');
checkBoxes.forEach((cb) => {
  cb.addEventListener('change', checkButtonStatus);
});
function checkButtonStatus() {
  const checkedCount = [...checkBoxes].filter((cb) => cb.checked);
  submitButton.disabled = checkedCount.length !== checkBoxes.length
}
checkButtonStatus();

how to enable button after checked

<input type="submit" name="sendNewSms" class="inputButton" id="sendNewSms" value=" Send " />

<input type="checkbox"  onchange="document.getElementById('sendNewSms').disabled = !this.checked;" />

Disable button if one of the checkboxes are not checked

<input type="checkbox" id="document-checkboxid" />
<input type="checkbox" name="VAT" id="accepttermsandcond-checkbox" />
<button type="button" id="startusing-button">CreateSubscription</button>