Question Laptop won't turn on. Help?

[SImoSere03]

I have an "old" laptop, it's a 2015 Lenovo B50-80. Some days ago I disassembled it to fix some problems i had with the screws and do some maintenance. I pretty much dissasembled everything to replace the old thermal paste. I riassembled it yesterday but now it won't turn on. if the battery is plugged in the power on led will turn on and then turn off again, if only the ac power is plugged in the charging led turns on but not the power on led. I have disassembled it now and i'm trying to find out where the problem is. In both cases (on battery or plugged in) nothing happens other than the leds, fan doesn't spin and monitor doesn't turns on. Can someone help me, I'm pretty sure i did everything right, I'm a computer engeneering student and I need it for some classes. If you have any ideas please write, i also have a multimeter in case i need it and i have another Lenovo B50-80 that was my sister's laptop in case i need some replacement parts.

EDIT: now when plugged in it behaves the same as on battery

 

[COLGeek]

Does the other laptop power on?

 

[SImoSere03]

Does the other laptop power on?

Yes it perfeclty working, i know that in case i could move my ssd and I'm good to go but I would prefer to fix this one.

 

[COLGeek]

Sounds like you either didn't reconnect something properly, or you damaged the device when disassembling/reassembling.

You need to retrace all steps you followed and verify all cables/connectors are properly attached. This means taking the system apart again.

 

[SImoSere03]

Sounds like you either didn't reconnect something properly, or you damaged the device when disassembling/reassembling.

You need to retrace all steps you followed and verify all cables/connectors are properly attached. This means taking the system apart again.

Thanks for helping me, I reattached all the connectors and cables and it still wasn't turning on. Then as a last attempt i reattached another time some of the connectors and then i reseated the ram and cleared the cmos. I don't know what the problem was but now it works again. Thank you so much for replying and helping.

 

[COLGeek]

Glad you sorted it out. Good luck.