Use Simplified Chinese Input Method: You can switch to Simplified Chinese Input Method in the input method settings of your mobile phone. Please make sure that your input method is set to "Simplified Chinese" instead of "Traditional Chinese".
Switch languages within WeChat: WeChat provides language setting options, and you can set the language to Simplified Chinese. The specific steps may vary depending on the version of WeChat, but you can usually find the option of "Language" or "Country/Region" in the setting menu of WeChat, and then select "Chinese (Simplified)".
Avoid copying and pasting traditional Chinese characters: If you type words by copying and pasting, make sure that you copy simplified Chinese characters instead of traditional Chinese characters.
Manual input in the chat input box: Enter the desired simplified Chinese characters directly in the WeChat chat input box, instead of copying and pasting.
Check the system language setting: Make sure that the language setting of your mobile phone system is also Simplified Chinese, so as to ensure that the entire mobile phone interface uses Simplified Chinese.
If you still encounter problems, you can carefully find options about language and input method in the settings of WeChat or mobile phone system. Please note that the specific steps may be different depending on the version of WeChat and the brand of mobile phone. If you can't find a solution, you can also search for relevant information on WeChat official website or social media, or consult WeChat customer service for help.