"But you were looking!"
Translation:Ty ses ale díval!
no, that was not the problem. czech has a pretty flexible word order, except when it comes to something called the "clitics". you just ran into the complexity of the czech clitic system here.
"ses" is an obligatory enclitic (a word that follows something) that belongs in the second position in the clause, after the first complete unit of meaning. the problem with Ale ses dívala. is that "ale" is one of the conjunctions (also including "a" and "i") that do not count as the first unit of meaning. so you would actually have "ses" as the first word, which standard czech does not allow.