Answer: Lack of bloom in viburnums can be due to too little sunlight (they do well in full morning sun or very bright dappled light all day) or to pruning at the wrong time of year, or in the case of a new plant it may still be settling in and becoming rooted and established.
Viburnums usually do not need much routine pruning as they have a fairly symmetrical natural shape. Any pruning for size would be done right after it blooms, reaching deep into the shrub to remove the longest branches but not taking more than 25% of the plant at any one time. I would not prune in late summer or fall because this can stimulate late season growht that will be late hardening and make the plant prone to winter cold damage. As you might guess, in the long term pruning to keep it small is probably a losing battle. It sounds like you may have planted it in a spot that is not large enough to accommodate its mature size -- viburnums typically take five years or so to begin to reach their mature height and width.
Unfortunately I am unable to check the mature size of this particular viburnum for you as "eastern snowball" is not something I am finding in the usual lists of common names. There are many different viburnums, so if you have the botanical name for it you could check, possibly at the Monrovia on line catalog descriptions
or at the Kemper Center web site
You may need to cut and paste the complete url into your browser ot make it work correctly. I hope this helps.
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