Roon remote in iphone x or samsung galaxy s10plus does not hold connection with roon core in Windows 10 PC

Hi, I have set up my roon core in windows 10 laptop. I have downloaded and installed roon remote in my iphone x and samsung galaxy s10 plus. when i start roon core and then any one of my roon remote, it identifies the core but does not hold the connection to proceed further. Please help.