W168 start error

[Mizdavilly]

Hi everyone. I have a mercedes benz A class w168 and I had it for years and nothing wrong with it , the other day while I was starting it up it the engine revolved slowly as of it was a cold start it moved but when I tried to start it again it showed start error massage.
What I have done so far is tried to resynchronize the key with the car but the alarm was working fine even before, then took the VDO and the key to a local shop the guy said they were synchronized.
what could be the cause and how can I fix it since the merc dealer ship here won't touch it

 

[Blobcat]

Hello and welcome

Sounds like the car battery needs charging / replacing

 

[Mizdavilly]

Hello and welcome

Sounds like the car battery needs charging / replacing

That was my first reaction , charging the battery and ultimately replacing it but no dice.
What are the causes of start error other than key fob / mmo
Could the starter be the issue ?