An answer devoid of numbers is useless. A symptom of posts without knowledge.
For example, one more useful suggestion discussed 120 volts at 126. That means light bulbs burn out twice as far. Completely ignored by line conditioners. If that same voltage is 135, then light bulbs burn out four times faster. Again, the line conditioner does nothing. But then the line conditioner was recommended without any technical facts.
Now lets start with important symptoms. For example, are lights changing in intensity especially when major appliances (dishwasher, refrigerator, etc) power on or off? If yes, your computer and light bulbs may have been 'canaries in a coalmine'. Reporting a serious human safety issue. And again, the line conditioner does exactly what it specs claim - ignore the problem and do absolutely nothing.
Second, you must confirm earth ground exists. Lights can illuminate while a serious problem remains. There is no way to test for this. You must visually inspect. Essential is a quarter inch bare copper wire that exits the breaker box. Must connect outside to an earth ground rod. Does it exist? Is it properly (firmly) connected to that rod?
Also another bare copper ground wire must connect the breaker box to where the cold water pipe enters the building - on the earth side of the water meter. Is that wire also firmly attached?
Important questions necessary so that the few more knowledgeable posters can actually provide assistance.
That line conditioner does not claim to solve what your symptoms imply. In fact, numbers suggested by your symptoms also say a line conditioner will completely ignore the problem. Problematic numbers are too small for a line conditioner to even see. But to better know, first some important facts must be provided in the above questions.
Do not take this lightly. In at least one rare case, the homeowner ignored the strangeness. Fortunately no one was home when the gas line exploded. Safety is so easily accomplished. And the few who post usefully also provide numbers. If that line conditioner did anything, the recommendation would also include a number that says why. Better is to provide answers to the above questions so that one with necessary knowledge can provide assistance.