Does "attention" have a plural form?
Attention is a mass noun.
attention
NOUN
[mass noun]
Notice taken of someone or something; the regarding of someone or something as interesting or important.
‘he drew attention to three spelling mistakes’1.1 The mental faculty of considering or taking notice of someone or something.
‘he turned his attention to the educational system’
Mass nouns, from Wikipedia:
In linguistics, a mass noun, uncountable noun, or non-count noun is a noun with the syntactic property that any quantity of it is treated as an undifferentiated unit
Basically, what that means is that whether it's one person's attention or the whole world's, it's always attention.
The plural form, in my experience, is used when one person does multiple, different things for another. Consider this excerpt from The Legend of Sleepy Hollow by Washington Irving:
Old Baltus Van Tassel moved about among his guests with a face dilated with content and good humor, round and jolly as the harvest moon. His hospitable attentions were brief, but expressive, being confined to a shake of the hand, a slap on the shoulder, a loud laugh, and a pressing invitation to “fall to, and help themselves.”