1. code error: the contents of the text box may not be updated correctly in the code. Please check the code to ensure that the name of the text box and the assignment statement are used correctly. For example, if you have a text box named "TextBox 1", you should use "TextBox 1". Text=' new content' "Update its contents.

2. Thread problem: If the contents of the text box are updated in different threads, you will not see the updated contents due to the thread model of VB. The UI thread of VB is separate from your worker thread, so if you try to update the UI elements in the worker thread, you need to use a special synchronization mechanism.

3. Synchronization problem: If the code is performing some time-consuming operations (such as network request or big data calculation) before updating the contents of the text box, it needs to be executed in the background thread to prevent the UI thread from being blocked and the text box cannot be updated in time.