Value for Dropdown selection not being posted on form Submit

Expected behavior

I expect the value of a selected menu item to be POSTed when the form is submitted.

I have no JavaScript code acting on the dropdown menu item at this stage (eg to set a value on hide.bs.dropdown being triggered)

Actual behavior

I have tried naming all elements of the dropdown with none posted. The aaa, bbb and zzz elements of the code below are temporary intended to help me make it work. They were added progressively as I found the value not to be posted.

Resources (screenshots, code snippets etc.)

      <!-- Timeframe Range -->
      <div class="dropdown" name="aaaa">
        <button type="button" class="btn btn-primary dropdown-toggle" name="rRecommendationsTimeframe" id="rRecommendationsTimeframe" data-toggle="dropdown"
          aria-haspopup="true" aria-expanded="false">Most recent</button><label id="rRecommendationsTime">7 days</label>
          <!-- Timeframe Options -->
          <div class="dropdown-menu dropdown-primary" id="zzzz" name="zzzz">
            <a class="dropdown-item" name="bbbb" value="7">1 Week</a>
            <a class="dropdown-item" name="bbbb" value="31">1 Month</a>
            <a class="dropdown-item" name="bbbb" value="90">3 Months</a>
            <a class="dropdown-item" name="bbbb" value="183">6 months</a>
            <a class="dropdown-item" name="bbbb" value="365">1 Year</a>
            <a class="dropdown-item" name="bbbb" value="730">2 Years</a>
          </div>
      </div>