Send turns into Send Later if you go offline. By default, TB will 'Automatically follow detected online state', in Tools/Options/Advanced/Network & Disk Space/Offline. So, there may be a problem with your network adapter or connection. Right-click the network icon in the notification area, Troubleshoot problems.

If I change the Automatiically to Manual and click on one of the next options would that clear problem ?

I don't know if it will help, because I think the issue is with the connection, not how TB recognizes it.

SFHowes, Appreciate your guidance given so far. Earlier you wrote "Send turns into Send Later if you go offline." I am rural subscriber and occasionally the circuit drops out. The TB problem usually appears in the morning. Perhaps I am causing problem by not shutting down my TB at night. I simply walk away from pc and it goes into standby. Then if my provider goes offline during the night ………..?

There is an online/offline status icon in the lower left corner. It looks like 2 monitors. If it has an x on top of it you are offline. Clicking the icon changes states assuming you have a working network connection. I suggest you check that icon periodically.

If TB is not automatically going online after a network interruption has temporarily forced it offline, you could try changing a preference in Tools/Options/Advanced/General/Config. editor. Double-click network.manage-offline-status to false. I can't say if this will have a positive effect or no effect at all, but it is easy enough to toggle it back to its default value, true.

Being in a rural setting the service is not always solid. Thanks to sfhowes and Truman I now have a better understanding of TB. Thank you both.