Possible Issues related to Multi-Variation:
a. You used more than one colon in variation specifics
b. You did not use colon in variation specifics
c. You used spaces between colon and variation specific value
Solution:
If it is a problem in one variation, you can revise the specific variation.
If you have more than one variations with this problem, you can export datasheet to Excel, use "replace" function to solve the error.