In frontend im trying to add product to cart. but its displaying error message This action could not be completed. Please try again in a moment or contact the service desk if the the problem persists

Check the network tab of your web debug tools in the browser if the request failed and if so what was the error message. If this is locally you should get a trace as response from the failing request which either tells you what the issue is or can be pasted here to get further help.

this error message is not part of the spryker demo shop. since it's a custom error message, it's very likely that there is some custom logic in place e.g. communication with a 3rd party system. I would suggest to debug the add to cart call and also check all the plugins which are executed