After Disassembling and cleaning my Laptop, It Won't Bootup

Hello,
Guys I have acer aspire 5750g laptop which a 5 year old but it works just fine , yasterday I decided to clean it up from dust so I disassembled it and cleaned it ,here where the proplems comes after cleaning it I start it and worked but my gpu didn't run so I disassembled it again to see the problem and didn't find any thing so I run it again but nothing worked ... My Lap even didn't boot it just turn on that blue light small lamp(power lamp) for 5 SEC and nothing happen no fan spinning or anything else
Please help asap , thank you