After debian upgrade 8->9 Server returned nothing

Hello,

we upgraded debian 8 to 9. After die Upgrade we reinstalled with the new OCS Server 2.6 (2.4 before) version. the webinterface works but the windows clients can't connect to the server.

Log of windows agent

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Starting OCS Inventory NG Agent on Tuesday, September 24, 2019 13:11:24.
AGENT => Running OCS Inventory NG Agent Version 2.4.0.0
AGENT => Using OCS Inventory NG FrameWork Version 2.4.0.0
AGENT => Loading plug-in(s)
AGENT => Using network connection with Communication Server
AGENT => Using Communication Provider <OCS Inventory NG cURL Communication Provider> Version <2.4.0.0>
AGENT => Sending Prolog
ERROR *** AGENT => Failed to send Prolog <Server returned nothing (no headers, no data)>
AGENT => Unloading communication provider
AGENT => Unloading plug-in(s)
AGENT => Execution duration: 00:00:00.

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apache error.log

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[Tue Sep 24 13:14:32.734363 2019] [core:notice] [pid 25420] AH00052: child pid 25555 exit signal Segmentation fault (11)
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Really need help, thank you in advanced