I would think if it says spendable, then you should be able to buy tickets. Try closing and restarting your wallet as it sometimes needs this to refresh. Also it takes 256 blocks (~1 day) for your stake reward to be returned and spendable.
Thanks, I guess although it says my DCR are spendable it needs more blocks to pass before I can buy tickets again. It now says need expiry beyond next height....
I am facing similar problems regarding stake mining / ticket purchase:
It worked quite fine for me during the last few weeks but recently two strange things keep happening:
1. I have the funds (108 DCR) to buy 3x tickets @ 33,12 DCR (it shows as "spendable" in my account). But when I try to buy 3 tickets I get an error "insufficent funds". Even for two tickets I seem to not have enough. I can only buy one. Why is that?!
2. Often I buy a ticket and and a few hours later the DCR I "spend" to buy the ticket are back in my account and I don't have a mining ticket.
Thanks for any help.