We first choose Vietnam, then have to switch to Taiwan

We have decided to travel to Vietnam.  Now it is time to choose a date.  Oops, my airline does not travel to Vietnam, so we change to Taiwan.  The cost is 35,000 bonus miles.  When I click on the purchase ticket link, the cost switches to 75,000 bonus miles.  Now I do not have enough miles to purchase tickets.  I will wait until tomorrow and try again.  I am hoping it is a glitch in the computer system.