I think this might help someone to understand why sometimes it takes longer to receive your donations or maybe one of the main reason other than error with email or amount in transaction. 
c/p
Every bitcoin transaction that's sent flows into what's called the mempool (short for memory pool) before it can be confirmed by miners. When there's a dramatic spike in transaction activity, the mempool can become congested because so many transactions are waiting to be included in the next block.
Bitcoin users across the network may notice their transactions sit as unconfirmed or pending for a longer period of time, and we understand this can cause users to be concerned about the status of their funds.
In most cases, your transactions will eventually confirm. It may just take longer than usual to do so.
see video for more info to understand.
c/p
Every bitcoin transaction that's sent flows into what's called the mempool (short for memory pool) before it can be confirmed by miners. When there's a dramatic spike in transaction activity, the mempool can become congested because so many transactions are waiting to be included in the next block.
Bitcoin users across the network may notice their transactions sit as unconfirmed or pending for a longer period of time, and we understand this can cause users to be concerned about the status of their funds.
In most cases, your transactions will eventually confirm. It may just take longer than usual to do so.
see video for more info to understand.
Code:
https://youtu.be/JtcchPVWxJ0