To fix Error Code 131026 in AiSensy, which means a message couldn't be delivered, you must make sure the person you're trying to message has the latest version of WhatsApp, check that their phone number is correctly set up on WhatsApp, see if they agreed to the latest rules and policies, and consider whether they are getting too many marketing messages from you in a short time. If the problem continues, reach out to AiSensy’s support team.