Adding my voice to say I am also having this issue. It was working fine last week? and has worked perfectly for years.
I tried different types of browsers, creating a new template, using a different sheet, editing the job and creating a new job entirely, and tried only merging about 10 rows.
The only thing that worked was this, multiple output mode to pdf. And then merging the files so I could print all at once.
The merge job took a lot longer (plus I only tried merging 12 and then 18 at once to get my full 30 files done) and downloading and organizing and the third party website and etc takes a one click job into like 30 clicks.
But... It worked. And it was faster than manually entering in all the information 30 times. So. There is that! Thanks.
Also following to hear if this gets seen/fixed/worked on/etc