Bootstrap 5 no longer uses the btn-block class to create full-width buttons.
To create a full-width button you will need to wrap the button in a tag that has a grid class i.e.: d-grid (grid display class)
01: <div class="d-grid">
02: <button type="submit" class="btn">Submit</button>
03: </div>Here is another article you might like 😊 "Be careful with HTML ID attributes"