It is not a system issue, it happens to me every day, for the past 15 days or so. When you play everything, close all the apps that you have been playing and then open them individualy. Your coins will be there. And since I see there are still people who can't find proper games, here is my daily routine:
Simple Hangman - play (lose on purpose) 30 games
Simple Hangman for Spanish Learners- play (also lose) 30 games
Be Happy - click one of the arrows 100 times
Gnar bike trial - get gold on 1 level or get silver on 1 level and play 3 in total
These apps will give you 135 coins in total. It takes me around 7-10 minutes, I've measured time. I would also suggest that you count games, since it is not always going to show you immediately that you have finished a task. I then do what I wrote at the beginning and all my points are there. If someone knows a faster routine, share it with us!