I have not changed anything in my code that used to run without this error. The transactions, once approved, still work fine.
The warning I get from phantom wallet is:
Unable to simulate. Make sure you trust this website since approving can lead to loss of funds.
I tried this both with a transaction that involves my custom program, as well as with a transaction that is just SystemProgram.transfer(). Both give me this warning.
I have also tested with this site on devnet: https://solana-twitter.netlify.app/#/ which was not written by me, and in the past it did not give me a warning, yet now it does.
Is there any way to get rid of this warning? If you need more information please let me know.