There are a few reasons you may not be awarded an Extra Turn which aren't caused by bugs.
We commonly receive bug reports about not receiving Extra Turns when making 4-5 Gem matches which can be caused by a number of reasons. If you still think you have an issue after reading this check out the instructions below to report it.
The most common reason you won't receive an Extra Turn is if one of your Troops is frozen.
When a Troop is frozen, no Troop on your team will receive an extra turn when you make 4-5 Gem matches with the frozen Troop's Mana Color. The order of your Troops doesn't matter. Troops which have Spells that grant Extra Turns (Such as Princess Fizzbang) also won't receive the Extra Turn from their Spell if they're frozen.
If you cast a spell with your Hero and your Hero's equipped Weapon has an Affix which explodes Gems, the Gems will explode before your matches are made because Affixes are calculated before the game board is checked for Gem matches.
For example: if your spell creates Blue Gems and you see a 5 Gem match was created, but your Weapon explodes 2 Gems, the Gems will Explode first. If the 5 Gem match is partly or fully exploded then you won't get an Extra Turn because the Gems were destroyed before the match was calculated.
This is currently the battle execution order as designed, however, the team is aware of feedback from players requesting affixes be calculated after Gem matches and will consider this for the future.
4x Animation Speed
Even if you are experienced playing on this speed, sometimes the turn is over so fast it's easy to miss what happened on the board (such as those exploding Gems mentioned earlier!).
But none of these explanations apply to me!
If you feel that the reasons above don't explain why you didn't receive an extra turn, please try to capture a video of the issue and report a bug with a link to the video. You can also contact support.