Moer
You're using a fine grind? I've always found grinding it myself to extra-fine works best for cold-brew. – Bruce Alderson
e
I pour it through a standard mesh a few times, then a mesh + cone filter. The resulting coffee is thick, dark, and has very low acidity (very nice over ice with a spot of condensed milk). – Bruce Alderson
Idade do feijão
If the beans themselves have been sitting on the shelf for longer - it means they have lost a lot of their fresh, volatile flavours. May not be the only reason - but it definitely affects the flavour you'll get. – Taryn East
Temperatura
Is the ambient temperature cooler, perhaps? It doesn't sound like you moved, but maybe it's a cooler beginning of summer, or you're using more AC? [...] – Jefromi