Originally Posted by
malgudi
Sure
SFO-FRA-SFO, bought a M-fare ticket on ua.com ... but when I try to request an upgrade, get the not eligible message.
Can happen if there is an existing upgrade request in place or you have been upgraded.
Other conditions, a bulk fare purchase? But those are not available on ua.com.
There are other non-published fares that have restrictions.
Or a simple IT glitch, a call to UA will probably provide more information.