You have done the only thing you could do and hopefully it will solve the issue.
You may need to use tow coats and the new Thomsons Water seal in my opinion isn't as good as the solvent based original.
There is nothing to be gained from tanking the inside as any water that gets in from outside would just blow the tanking off.
In my garage, I also lined the inside with polythene then added battens and attached flooring grade chipboard to line the inside keeping moisture behind and have had a dry internal wall for 20 years and have a wooden wall for easy fixing!
Given you have ponding on the floor, I would check if there is not a leak to the roof or any flashings.
You may also have partially filled mortar joints enabling the water to penetrate more easily.