146: Unrecognized file type

You started a block with a file token […] which announces an embedded file where … stands for the file type and an optional argument. However, the specified file type is not recognized.

Solution

Make sure to use a recognized file type suitable for embedded files – these are a, b, d, h, p, q and t. If you did not mean to embed a file, you can prepend the first square bracket with a backslash: \[…]