There have been multiple attempts at scaling Bitcoin on-chain by raising the blocksize. They have all been unsuccessful because they have been blocked by the Core developers and their supporters using censorship, troll campaigns, ddos and abuse. It's not due to technical reasons but because they want to redirect scaling off-chain, using technology they coveniently develop. The very same developers actually supported bigger blocks a couple of years ago but changed their tone to support the scaling approach their company favors. After the last attempt (Segwit2x) it's clear Bitcoin won't scale on-chain.
However the technical limits of the technology ha never been reached, tested or even been fully researched. Bitcoin Cash is for example a fork which aims to scale on-chain by increasing the block size. If all transactions from Bitcoin would be done on Bitcoin Cash the network would work fine today.
Where the actual limit is we don't know. It's probably not possible to support every financial transaction for everyone. For that we do need off-chain scaling in addition to many other improvements.