This happens often and can be frustrating, but it makes sense internally. It's not that the platform "doesn't want" to spend your money; it's simply following rules that aren't always obvious.
1. The logic behind what's happening
When you set a high budget ($120-$150 per ad group) from the start, the system has to quickly find a lot of quality impressions or clicks to justify that daily expenditure. If your audience is very specific, or if your initial bid (even if it's automated) isn't competitive enough for that volume, the system gets stuck. It can't spend all of it because it doesn't find enough opportunities that meet its internal profitability criteria.
By lowering the budget to $10-$20, you're essentially telling it, "I only need a little traffic per day." That's much easier to achieve. The system quickly finds those few impressions and spends the budget. *But* if you're not even spending $10-20 on some groups, it's a key sign: that particular audience is too narrow, or the creative/offer isn't resonating. Most likely, it's not just the budget, but a combination of three things:
1- Very small or overlapping audiences.
2- The platform's spending pacing.
3- The learning phase: Every time you create a group or drastically change it, the system enters a trial period. If during this phase (around 24-72 hours) it doesn't consistently achieve enough conversions (or clicks, depending on the objective), it gets stuck performing poorly and doesn't dare to scale.
Forget about reaching $150 for a moment. The goal now is to stabilize your spending and then scale. I suggest this:
a. Review your audiences.
b. Don't have 10 "inactive" groups.
c. Scale gradually, not aggressively.
When a group consistently spends its low budget (for example, $20) for 2 or 3 consecutive days with stable performance (a CPA or cost per click that doesn't skyrocket), increase their budget by a maximum of 30%. Go from $20 to $26. If they spend it all again the next day and performance remains stable, increase it to $34 the following day, and so on.
If at any point they stop spending, revert to the previous budget where it was working and leave it there for a couple more days before trying again. This method is called "gradual scaling" and is the safest way to grow a campaign without the system spiraling out of control.
