This happens because of stacking of bids of the already existing bid adjustment in the campaign. When we show a suggestion of bid change, we take into consideration the current performance which is based on your currently existing bid adjustment. I have explained it mathematically below:
If there is an existing bid adjustment of say, 35% and you've set the range as -50% to 50 in "Set bids", your new bid can vary from (-50%+35%) to ( +50%+35%) i.e.a range of -15% to +85%.
The "Set Bids" option can suggest the same bid adjustment for all campaigns if the calculated bid adjustments for all your campaigns is greater than the allowed range for min-max. adjustment.
For ex, in the screenshot below, the range defined is -50% to 50%, and the bid adjustment calculated by the tool for all the campaigns is greater than 50%. Then, a bid adjustment of 50% will be suggested for all the campaigns. Screenshot below.
To fix this, you can either increase the "allowed change%" or alter your goal value.
If you choose a Conversion based metric (like Cost/Conv or Conv. Value/Cost), the system will only recommend bid adjustments for locations with conversions.
You may not see all the campaigns in the Geo Bid Adjustment optimization if you have campaigns which have had less than or equal to 5 clicks in a selected location for a selected date range. This has been incorporated in the tool to reduce noise and make sure you're viewing data that has some significance. If you increase the date range, you'll notice that the number of campaigns shown increases as they have more data for a longer date range.
The tool may show "N/A" bid recommendations if the bids for the campaigns were recently updated. Showing N/A is a fail-safe check to avoid stacked bidding for devices/locations which recently had a bid adjustment in last 14 days.
If you still want to update bids for such locations/devices using Geo and Device Bid Adjustment, you can toggle tab to "Yes" for the setting "Update Recently changed Bids". This will let you set bids by removing the "N/A".
The Geo and Device Bid Adjustment tool only looks at data for ad groups that are currently active. This is because you don't want to set bid adjustments for entities that are active based on data from paused entities. In AdWords, the data for ad groups that are paused is also included. Therefore, you might see a difference in data in the tool and in AdWords.
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