Are the keys from the input table already in the destination table? Are you supplying the entire key (if multiple fields in the key) from the input table? If neither of these ideas solves your problem, then you next post should be what the key fields are in the destination table, what the fields are from the input table that are being used to fill the key fields in the destination table. Give us both the field names and the field definitions.
Please post the exact message displayed. From memory I think the message shows how many records were not appended for various conditions. You maybe appending blank fields, incorrect data type etc.
Use the "Go Advanced" button just below the "Quick Reply" area. In the "header" area of the message field, you should see a paper clip icon. Click the paper clip icon. Then in the manage attachments form, click the "Browse..." button. Navigate to the image on your computer, select it and click the "Open" button. Then, before leaving the "Manage Attachments" form, click the "Upload" button. I have done all that is documented here, and there should be an attachment to this post which will be a small image of Snoppy. Just to be sure, I clicked the "Submit Reply" button that is below the "Additional Options" area rather than the "Submit Reply" button that is below the typing area for your post.
If you preview your post you will be able to see if anything is attached or not. Of course, you could also, carefully, retype the message you are trying to attach. That might just be easier for all for you to take the time to do that typing of the message if the attachment process is not working for you.
What worked? The query or the attachment?
By the way, having seen the attachment, there is a ton of information in the error message rather than what you "quoted." The message states that Access "can't append all the records in the append query." That means that not ALL the records were appended. It does not mean that ALL the records were rejected. When it states that "not all the records were appended." that means that some records were not appended. Then the message gives you the count of the records that were not appended and why they were not appended. That is why I asked for you to "carefully" retype the message so we could see what the message actually says. It is impossible (usually) to help someone with only a small portion of the information. And even harder to help someone that is not sharing ALL the information that is being requested. If I am sounding a little unhappy here, it is because I have been using my time to try to help you, but you have not been careful of my time.
Now, going back to something I asked for in my first reply to you.
If neither of these ideas solves your problem, then you next post should be what the key fields are in the destination table, what the fields are from the input table that are being used to fill the key fields in the destination table. Give us both the field names and the field definitions.
If you want help from me, then answer the questions. If you don't care about me helping, then don't answer the questions.