Try delete the Activity and reinitialize it, then try it will work or not. Before trying it update the UiPath.System.Activities package and select the lowest as applicable option in Runtimerule option in Manage packages.
Thank you for your help… I deleted the activity again, felt for the 10th time BUT I had the packages in preview that was perhaps a mistake, have now downgraded the packages by 1 version and suddenly it worked!