You need soft water with soap.
Soap and soft water created suds.
If no suds, then hard water.
If hard water, then soap reacts with minerals in water to create curds.
If curds, then gray clothes.
If there are soap and suds in the washer and then suds disappear, then that means there are very dirty clothes in the washer or enough soap was not used, and more soap is needed to keep dirt suspended.
I have used grated Fels Naptha and STPP in my frontloader. It is very difficult to get just the right amount of suds, and we have medium soft water here.