Feb 28, 2020, 13:5402/28/20
This sounds like the same issue as the frequently asked question of not having enough food.
I think you might find that your production of silver has shut down because you have reached the maximum storage amount of your town.
504,714 silver per hour is what you can produce, only if the storage limit is not exceeded.
I think you will find the increase of 1.9 M to and now only 2.1 after 4 hrs is probably down to acquired silver from tiles or tasks etc