airline refusal of passengers due to 'no visa in passport'

we were at singapore airline flying with scoot airlines from singapore to qingdao, direct flight. we had tickets to fly qingdao-shanghai-amsterdam (all on one day) 48 hours after our arrival. we had an invitation letter form the company we were visiting.
scoot airlines staff at the counter refused to give boarding passes or even to process this. the airline staff just declined, declined, declined every discussion. after long arguing, the desk supervisor came and did the same. they gave first a reason they are only a point to point airline (while the qingdao flight continues on to another scity ….), then they said the stop in shanghai (just transfer) is not allowed….
after discussion they simply stopped discussion and ignored our presence at the counter. calling the call center did not change anything, since they referred us every time to the counter.
scoot simply said that VOA is not possible
refund of the ticket at the counter or a confirmation that we were there was not possible
scoot airline staff simply ignored us further on and did not make any attempt to resolve this
do airlines not know about the 72h free transit option ?