No H2S detection in NGA Analyzer

We use Agilent NGA Analyzer GC based on 4 column configuration. Hayesep Q pre column, Hayesep Analytical column, molsieve column for TCD and one capillary column for FID. The H2S elution takes place in the Hayesep analytical column. But now a days our H2S response is too slow that it is not detecting even 1% H2S in Gas samples. Kindly advise how to make the H2S response in a proper way. The valve timing and configuration are attached. 

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