"This ring has (a) great sentimental value for me."
I do not see any differences in meaning between the sentences with and without the determiner.
Magda wrote:Hi,could you tell whether my sentence requires the indefinite article?"This ring has great sentimental value for me."Thank you
I prefer it without because it refers to value. Is of value is the normal expressions.
Hello Magda
"To have value" is a set phrase. So I would omit the article here.
MrP