If I set "Cut-off days" to 60, does it mean that only users who have shown some activity in the last 60 days will receive a greeting? How can I disable this so everyone gets a bd greeting? ( i see max is 720 days)
I do think that I found it. At least I can put now in ACP higher numbers than 730 in this cut-off field.
Go with phpmyadmin in your database. Make a search for "birthday". Open the table "xf_option". See the row in green. Click on on the left on the pencil and change the number "730" in the red box on this screenshot to whatever you want it to. I put 10000 in that field.
Then go in Xenforo/ACP/options/XenFacil Birthday Greetings and change the number in the field for cut-off days to any number below i.e. 10000 (or whatever you set your maximaum in the database)