cant view topics ans non admin bbpress

hey,

i use wp 4.6 and bbpress 2.5

my users cant view forum posts

"one line says the forum has 3 topics"
the next line says
"sorry no topics were found"

when i view as admin everything looks fine

i selected "automatically assign users the participant role"

i found that after wp 4.0 something changed with wp <> bbpress
i downloaded a "fix" - that did not help
these posts are between one and two years old anyway

any ideas?
thanks