Gzip from c# to java decoding from b64 issue

[shandowspy]

Hello.

I receiving base64 String contains gzip file, from our team working with C#.
When I trying to decode and open it with GZIP in Java I got this exception

Exception in thread "main" java.util.zip.ZipException: Not in GZIP format
at java.util.zip.GZIPInputStream.readHeader(Unknown Source)
at java.util.zip.GZIPInputStream.<init>(Unknown Source)
at java.util.zip.GZIPInputStream.<init>(Unknown Source)
at main.main(main.java:41)

Is there is some difference from base64 in C# and Java?
And how I can solve this problem?

Thanks in advance

[Norm]

Look at the file in a hex editor and compare its contents to a good file to see if there are any obvious differences.
What file was base64 encoded? The zip file or the contents of the zip file?