When having custom number format as:
[>=1000000]#,##0,,;[>=100000]#,##0.0,,;#,##0.00,,;[<=-1000000]#,##0,,;[<=-100000]#,##0.0,,

Add a semicolon at the end of the custom number format:
[>=1000000]#,##0,,;[>=100000]#,##0.0,,;#,##0.00,,;[<=-1000000]#,##0,,;[<=-100000]#,##0.0,,;