This could be many things but you can try the following fixes which might help resolve it:
Ensure you have enough SOL in your wallet to execute the transaction
Disable Adblock on Step.finance
Use Chrome or Brave browsers. This is what Step is tested on, other browsers may or may not work correctly.
Do a hard refresh on your step.finance page (see how to here)
Clear your browser cache for Step
It may also be the case there is an issue with the node Step is connecting to. Currently there is alot of traffic going to Solana nodes and due to this congestion of traffic it can result in failed transactions. The best solution here is to hard refresh and try again. The step team is actively seeking to setup our own node to alleviate this.