Hi @howie83149
If your multimeter's test lead probes are too thick to insert into the cmos battery cable plug's two small hollow connectors, try inserting some appropriately sized pins into them and place the meter probes on them. Make sure that the pins and probes don't touch each other.
If the battery voltage is <2.5V or if the battery is >4-5 years old, replace it. Search online for ''01HY008'' to find suppliers that suit you best.
An amber Power light indicates that the battery has between 5%-20% charge.
It may be at the lower end so try leaving the charger connected for 2-3 hours and check if the laptop turns on. It may be that if is is too low a charge, that the charger can't do both, i.e. charge the battery and run the laptop at the same time.
Did you try a power refresh with the battery and cmos battery removed? I suggest you try this after you have tried charging the battery for a few hours and not before.
If not, disconnect the charger if connected, disconnect the battery, disconnect the cmos battery and then ''press and hold the power button for 30 seconds'' and release.
Reconnect the cmos battery, reconnect the main battery, reconnect the charger and check.