"Gas estimation failed" on Ropsten using MetaMask!

Question

I'm testing a smart contract using Remix, MetaMask, Ropsten. Yesterday I developed my contract on Ropsten network and everything goes in the right way. Today I was developing the SAME contract code, but an error poped-up:

"Gas estimation failed Gas estimation errored with the following message (see below). The transaction execution will likely fail. Do you want to force sending?"

So, I developed my contract on Rinkeby and it worked fine. I send a request to the Mainnet too to develop the contract and gas estimation was ok, it tells me 5239423 gas.

I have to say that is not the first time that this error happens and every time it solves on its own. This time I would like to figure out, once for all, which is the cause, which is the solution. Could you help me? Thanks!

Answer 1

The block gas limit is decided by miners by voting when mining a new block. A new block can increase or decrease the block gas limit in 1/1024 of the previous value.

Networks like mainnet the gas limit is set by agreement between miners at 8M gas. Rinkeby (a proof of authority) has a gas limit set at 7.5M gas.

Ropsten is a test network with limited hash power, so the block gas limit varies a lot. I've seen it from 4.7M gas and up to 20M gas.