Unable to install apps

when i try to install a .bar file into bonita perfomence 6.3.6 i got:
This field file format is not allowed. Only ".bar" .
it had worked fine last year and my profile is administrator

error from bonita.log

2017-10-18 14:32:02 org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/bonita].[themeResource]
GRAVE: Servlet.service() for servlet [themeResource] in context with path [/bonita] threw exception [null] with root cause
java.net.SocketException: Connection reset by peer: socket write error

at java.net.SocketOutputStream.socketWrite0(Native Method)