/ad_account_id/insightsfields=campaign_id,campaign_name,reach,impressions,frequency,spend,cpm,cost_per_unique_outbound_click,inline_link_clicks,website_ctr,ctr,cost_per_action_type,actions,unique_actions,purchase_roas,outbound_clicks,account_currency,cost_per_thruplay,cost_per_inline_post_engagement,inline_post_engagement,action_values,conversions&use_unified_attribution_setting=true&filter[{"field":"action_type","operator":"IN","value":["mobile_app_install"]}]&action_attribution_windows=["1d_view","7d_view","1d_click","7d_click","28d_click"]&date_preset=maximum"

Here's the url campaign insights url example.

Getting the same error but in v19.0 version. Also It's not giving error in specific time range. Everytime when its giving an error time range is different. Below is the error response I'm getting.

{"error":{"error":{"message":"Service temporarily unavailable","type":"OAuthException","is_transient":false,"code":2,"error_subcode":1504018,"error_user_title":"Your request timed out","error_user_msg":"Please try a smaller date range, fetch less data, or use async jobs","fbtrace_id":"Afw2VzaAdO_5W7WZu7XVyOX"}}}