211: Missing whitespace after alignment mark
You started a line with an alignment mark such as
:: which was not followed by whitespace. But that is expected.
Make sure to have whitespace after an alignment mark. A single space is enough:
.:. And our journey to the center of the earth continued.
If you did not mean to set the alignment, but want to use these characters at the start of a paragraph literally, you can prepend a backslash: