Engine randomly starting after EGR replace

Hi guys,

I have a 2010 toyota Prius. 220K miles. Original hybrid battery.

I was having the famous morning rattling in the engine but coolant level didn't go down. I opted for cleaning EGR valve. After cleaning better but not perfect. I then replaced EGR valve.

Now car started and drove normal for about 10 min then gas engine wouldn't start. "check hybrid system" popped up. I feel it's because gas engine not cranking so hybrid running low on juice. I parked at gas station and was able to start engine. I drove and after engine went off it didn't want to start again. Turned car off and back on and engine came back on. Once the gas engine comes off and the the battery pushes the car, when the car wants to crank the gas engine won't crank and engine won't come on. I get all sort of lights on dash. I turned car off and back on about 3 times and was able to keep going (I was trying to make it to my house). Finally all lights came on and hybrid battery seems to be depleted to a degree so car is not starting now either in electric or cranking de gas engine. It's just reads "check hybrid system".
If it would be a normal circumstance, I would think it's the old hybrid battery, but since it happened right after replacing the EGR, I have my doubts.

This are the facts. Any input?