Welcome to OpenStreetMap.

Although adding oneway=no to a road is harmless, it doesn't actually change anything as that is the default for roads. There are cases where it can be helpful, as explained in the OSM wiki.
https://wiki.openstreetmap.org/wiki/Key:oneway

If you are experiencing problems with routing software, this may not solve them unless the router is badly broken. If it does, there is always the chance that another mapper will remove the oneway=no tag as unnecessary in the future. If you need help, it may be worth asking in the OSM Community Forum.
https://community.openstreetmap.org/