While trying to book HPTDC hotel (Kunzam at Manali) and bus tickets from (and to) Shimla from a HPTDC authorised travel agent at Calcutta today we found HPTDC bus reservation portal was giving an error message ("define routes" or something like that). When HPTDC was contacted over phone from that agency office we were told that HPTDC will not be operating in Shimla<-->Manali sector at that time (17-22 March) and we should rather look for "state transport". Our agent said "state transport" in this case mean HRTC.
My question is: are there any problems if someone books HRTC tickets in advance through HRTC portal? I mean, how reliable is HRTC?