DFP ads not always showing on all browsers - html

Question

We have implemented multiple ads on our site and it has been working fine since recently. We have not touched our line items but created a few new creatives which are currently displaying. However, since this change, we randomly end up with certain ads not showing at all causing blank spaces. We have not touched the initial code or ids. We have tried logging into user accounts and that seems to cause ads to load more often but we still sometimes sit with an empty space block.
I have tried to research this subject but cannot find a solution. I have tried the fixes stated by this site but it did not help.
I have also looked at this discussion where they stated the importance of having a user account, which seemed to help but we still sit with blank spaces instead of ads from time to time.
<div>
<script>
googletag.cmd.push(function() {
googletag.defineSlot('/191675786/bottom_mobile', [300, 250], 'div-gpt-ad-1470805011041-0').addService(googletag.pubads());
googletag.defineSlot('/191675786/top_mobile', [320, 50], 'div-gpt-ad-1470804718031-0').addService(googletag.pubads());
googletag.defineSlot('/191675786/bottom_widescreen', [728, 90], 'div-gpt-ad-1470804049204-0').addService(googletag.pubads());
googletag.defineSlot('/191675786/right_side_1', [300, 600], 'div-gpt-ad-1470775758148-0').addService(googletag.pubads());
googletag.defineSlot('/191675786/middle_mobile', [320, 50], 'div-gpt-ad-1490793232691-0').addService(googletag.pubads());
googletag.defineSlot('/191675786/right_side_2', [300, 250], 'div-gpt-ad-1470775758148-1').addService(googletag.pubads());
googletag.pubads().enableSingleRequest();
googletag.enableServices();
});
</script>
</div>
<aside class='adverts'>
<div class='mobile-advert text-center'>
<!-- /191675786/top_mobile -->
<div id='div-gpt-ad-1470804718031-0' style='height:50px; width:320px;'>
<script>
googletag.cmd.push(function() { googletag.display('div-gpt-ad-1470804718031-0'); });
</script>
</div>
</div>
</aside>
<aside class="adverts padding-medium-top">
<div class="widescreen-advert">
<!-- /191675786/bottom_widescreen -->
<div id="div-gpt-ad-1470804049204-0" style="height:90px; width:728px;">
<script>
googletag.cmd.push(function() { googletag.display("div-gpt-ad-1470804049204-0"); });
</script>
</div>
</div>
</aside>
<section class='rightside-container col-sm-4 col-xs-12'>
<aside class='adverts'>
<div class='mobile-advert text-center'>
<!-- /191675786/bottom_mobile -->
<div id='div-gpt-ad-1470805011041-0' style='height:250px; width:300px;'>
<script>
googletag.cmd.push(function() { googletag.display('div-gpt-ad-1470805011041-0'); });
</script>
</div>
</div>
<div class='widescreen-advert'>
<!-- /191675786/right_side_1 -->
<div id='div-gpt-ad-1470775758148-0' style='height:600px; width:300px; margin-bottom: 20px;'>
<script>
googletag.cmd.push(function() { googletag.display('div-gpt-ad-1470775758148-0'); });
</script>
</div>
<!-- /191675786/right_side_2 -->
<div id='div-gpt-ad-1470775758148-1' style='height:250px; width:300px;'>
<script>
googletag.cmd.push(function() { googletag.display('div-gpt-ad-1470775758148-1'); });
</script>
</div>
</div>
</aside>
</section>
We have not found any solution as of yet and we do not understand why it only show ads sometimes but not always. Correct me if I am wrong but if the code was incorrect, wouldn't that mean that no ads would show ever?