Why it matters
<input type=button|submit|reset> without a value or label is announced as an unnamed button, so its action is unknown.
How to fix it
Give the input a meaningful value attribute (its visible text) or an aria-label.
Example
<input type="submit" value="Subscribe">References
More accessibility rules
void a11y reports 48 rules in this category. WCAG 2.2 AA through axe-core, plus checks axe can't do alone: visible keyboard focus, 24/44px target size on mobile, 320px reflow and disabled zoom.
button-nameButton has no accessible namelink-nameLink has no accessible namelabelForm field has no labelselect-nameSelect element has no accessible nameinput-image-altImage button has no alt texthtml-has-lang<html> has no lang attributehtml-lang-valid<html lang> is not a valid language tagdocument-titlePage has no <title>